They didnt choose to expect this. They expected it because Universal hinted at something then didnt deliver.
As described earlier, no they are not. Or not at least unless you are changing the dictionary definition of preview. You can dance around this all you want but it is an inescapable fact.
A preview is a full viewing before regular attendees get to view it. Had Universal stated that they would getv "limited viewing" then this would have been different. By stating preview they are hinting at a full viewing before everyone else, they have not delivered that hence the anger of many people.
Since you keep referencing this elusive dictionary definition without actually producing one, I'll do it for you:
NOUN:
1. An advance showing, as of a movie or art exhibition, to which a selected audience is invited before public presentation begins.
2. An advance viewing or exhibition, especially the presentation of several scenes advertising a forthcoming movie; a trailer.
3. An introductory or preliminary message, sample, or overview; a foretaste.
TRANSITIVE VERB:
pre·viewed, also pre·vued pre·view·ing, pre·vu·ing pre·views, pre·vues
1. To view or exhibit in advance.
2. To provide a preliminary sample or overview of: The professor previewed the course for us.
The Universal preview fits definition 2 for sure and also fits definition one and three. No where in the definition does it say it has to be "full" (whatever that means anyway - people seem to be able to get a lot if not all of the land done in these two hours).
Then again, you didn't even know how a camera worked...
ETA: I agree that Universal totally messed this up, because, when booking back in February or so, they did not say this would only be a preview. Only after announcing the GO for June 18th, did they say it would be a preview. I just hated that people kept giving their own definition of what a preview is (without ever actually reading said definition), when clearly a preview can be as limited as a movie trailer (which I still call "previews") to as all access as an unlimited screening before the public. By calling it a preview they really gave themselves leeway on what they had to deliver. It just wasn't what people had initially booked.