If they let everyone in that line in (enough people to stretch from one side of the park to another) it would be anarchy. The opening would bottleneck, the lines to get into shops would go on for hours, there would pushing/shoving/fighting hourly, and you literally would be unable to move.
In regards to the "Disney" policy of letting everyone in, this isn't a single attraction. It's an entire land, one based on books that have been translated into 40+ languages and spawned the highest grossing film series in history. UO HAS kept Forbidden Journey open past closing for those in line, but the line to get into the land isn't the same beast. There aren't really set rules for setting capacity for an entire land and honoring place in line. Let's put it this way, if you get in line at 6 o'clock and it's a five hour wait, you'd better do some counting on your fingers. Not really that hard or unreasonable to figure out that if you get in line that late and it's still long line, then you might not get in.
Well, first, if they let normal guest flow through the area and utilized the attractions queues to do what they were designed for, they wouldnt HAVE those lines to let in.
Second, this is a Land, EXACTLY. Access to the land itself should be open, if you want to get in line for the rides, shows, even shops while they are this crowded, go ahead. But the land itself should be open. I REALLY dont think you would have the problem.
Simply: If I have to wait 5 hours just to enter the area, and once I am in, I am in, then Im staying as long as I possibly can, especially when I see 10-20 min waits for 2 out of 3 attractions and 1-2 hours for the premiere one - Im good for the day!
Heck, theres food, theres shopping, I may just stay all day and I get plenty to do - but it means someone else can not get in and is still in line outside the area just hoping to get inside.
If on the other hand I can pass through, look around, see that the ride wait times are longer than I want to wait, grab something to drink, etc, then Im somewhat satisfied and Ill move on which of course makes room for the next person (or persons).
If the line for the individual attraction (lets take HG for example) gets up to 50 minutes this way, it still has the same hourly capacity: difference is, MORE people are actually experiencing it, as opposed to me not wanting to leave the Land and deciding to ride it myself 4 or 5 times because its only a 10 minute wait and, well, Im in the Land and youre not, so too bad so sad!
When you look at it that way - the problem becomes more aware.
Also, I am not looking at this from a "Only Harry Potter Fans" outlook: I personally have stated many times I am NOT a Harry Potter fan, I am a Theme Park nut! So the "its an entire land...based on....blah blah blah" doesnt matter to me - the point is: its a Themed Land yes, with 3 Attractions and 2-3 Shows. And looking at it from that standpoint, (and a lot of guests do - not everyone is a Harry Potter fan, or a Comic book fan, or a Snow White fan, etc), and IOA being in the Theme Park business, they also need to consider the bigger picture.
So by restricting access to the entire Land, by queueing for admission to the entire Land instead of the individual attractions, you are creating the opportunity for the lucky ones who get in to stay in and enjoy the 10 minute wait for DC or the 60 minute wait for FJ over and over again, as long as they dont leave the Land. While the folks still out in line even to get into the Land have to wait for those people to leave.
As to the point that "it is an entire land based on...."
Weather or not it is Themed on Harry Potter, or on Santa Claus, it is NOT a seperate ticketed attraction or area- access to it by design should not be treated as such. Its just bad policy.
AND CONSIDER THIS:
And with TWO "E" ticket attractions and one of the few childrens attractions in the park at all, thats a LOT of real estate during peak season to just take "off the map" and limit access. And thats the problem: by doing what UO IS doing, they are not utilizing their attractions queues correctly, and are creating an "exclusive" area for those lucky enough to get in, thereby also limiting individual access to TWO major attractions!
See, from an Ops standpoint this is a horrible choice. May be great for the die-hard HP fan, but for the average TP day-guest, and for moving people around, bad choice.
That brings me to your next point:
UNLESS youre going to restrict access without a method of making sure everyone has the same opportunity to visit (some way to force people out after a certain period of time or restrict them to only ride the ride once a day,etc), or make it a seperate ticketed attraction, then you have to take this into consideration.
Look at it this way: I may not be a HP fan, I may be a roller coaster enthusiest: does that mean that I should have to wait 5 hours just to gain access to DC which has a posted 20 minute wait?
Is it fair or right to deny that guest access to the coaster (the single E-Ticket attraction) just because you re-themed the area to something they dont really care much about, but the folks who are already in there can ride it over and over with the 20 minute wait as long as they dont leave the protected area?????
Again - Ops nightmare!
For the argument you are leaning towards, WWoHP should be either a seperate ticketed area, OR there should be hard-ticketed "Harry Potter" events after hours. Then you could keep the intimacy. Otherwise, the same access and restrictions should be the same for WWoHP as it is for Marvel Island or Seuss Landing: area open and attractions have individual queue waits.