Don't know what you are smoking but that never really as a point of speculation.
Gonna defend Kevin when it comes to this--but I am gonna do so by comparing it to another IP that is being rumored with that of Five Nights At Freddy's.
Say if it was FNAF, if it was that of the film version from the 2023 outing--then they would be having the side walls done in a way that would be present at the edges of the building (And I know there are some who think FNAF are in H-Lot South, which, lol).
Assuming if Terrifier is in H-Lot and if it is the Funhouse, then so-far the openings match that of what is depicted from the film. Guests enter the house from the left side, while the right opening could be a section that could either be something guests can spot other guests from the outside from (like the Dead Exposure facade in a way); or--it is a opening for the sake of an Art The Clown actor to come out and interact with guests.
We saw them doing similar with Texas last year; and that worked in a similar way (but on the right side being the guest entrance point in comparison).
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As for what venue is actually being lost--the way the wood is being set up in SS12; I actually think it is that venue being the one lost instead of SS15 or UBE.
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From what it seems--they are currently installing a large circular wooden platform within SS12.
EDIT: If a post is made by the time I am doing this--then it will be a separate post but I figured it's worth stating for the obvious. SS15 is typically one of the later venues that begins construction for HHN--typically around that of Late June/Early July. Assuming they are expedient; SS15 should be stricken down in a quick and easy fashion within the Late May/Early June period.
That should give them plenty of time for the sake of DND's strike down so they can then prepare the venue for that of HHN's purpose (Murdy has also spoken that a portion of the queue will go into SS15 as it typically has [against my desire]
While I think UBE might be the more complicated of the sort--especially in part because they had the sets from Picard in and that it might be a small complication; I doubt it's going to cause them to fuss and worry about things in a way that causes them to reconsider location.
As it stands right now for SS12--the good side is that the major construction for Hollywood Drift's ride track and supports are now done. The exclusion of that being that of the half pipe shields and how they will block out sound. The NBCUniversal Creative Campus is also complete--meaning it should be easier now for studios to work around the area without concerns of that being a factor. They also have two sets of elephant doors for that stage, so assuming if say; Jurassic Overflow uses a portion of the area outside of SS12 for queue flow; it won't be as if the world will shatter and all civilization will fall to collapse.
Personally speaking--I think SS12 is just gone because of the fact that studios can use it again. Might this be a question in 2026, depending on how sound is muffled and blocked with the half pipe tunnels, and if it helps (or deters) the studios around Universal from using that stage? Probably. But I think for intents and purposes, SS12 is out of the event's hands now and we got SS12 due to a series of chance circumstances last year.