It has gotten a little ridiculous, and does boil down to the opinion of the appraiser. To the OP, I don't envy your "review" by any means. Good luck with that (not being facetious) I would not want that assignment.
Is a sales office/model C1 or C2? Me personally, most likely would consider it C1 but as always in our field "it depends." Mostly, to me, it's new construction and C1, but I guess I could see where it could be C2 because of "wear and tear" etc of people walking through (and yes, including Carpenters and other workers who originally worked on it) But most Models/Sales offices I've walked through (and I've done MANY, including just on Mon) the sales office/model is IMMACULATE, for obvious sales reasons!
To the OP, though, I'm sort of curious why you're being asked to review a report for UAD quality/condition requirements and not other "typical" appraisal/USPAP requirements... Can you expand? (not asking you to give up confidential info by any means)