These previews are orchestrated to test the park, ready Team Members in all positions, and tweak operations before opening.
I cannot stress to you how important the last two weeks have been to design the operational playbook for the park.
For example, not enough Team Members were frequenting dining locations, which made it difficult to test operations there, so they decreased ALL food prices by 50% to lure in more diners. That wasn't advertised or promoted; it was not a promotion to make money, it was to give cooks and front of the house staff more time to test and adjust service.
Behind the scenes, people at the top are probably desperately hoping that since these previews are in-house, and no one wants to lose their job, no one speaks too openly about the shortfalls of this STILL UNFINISHED theme park. No pictures are allowed because that can be regulated, but I am sure some within the company would prefer Team Members not talk at all about the rides they're experiencing that are still missing many effects, some animatronics, and are experiencing extended downtimes while they work through the kinks of full operations for the first time.
Is it good promotion to have the most enthusiastic among us visit first—who also are the least likely to say negative things about their employer? Sure. That's a good effect of choosing TMs to visit first. But is this run by marketing? Absolutely not. They're busy dripping out fun and cool new details every single day to the public, where they can control the narrative. Like yesterday's podcast, the recent in-depth Hollywood Reporter, and the big media day push later this month.
My two cents. I am not privy to all information though, so grain of salt.