I think the average guest truly doesn't see it. It is much easier for them to let go and really let themselves become part of these worlds. As theme park fans with a working knowledge of how these parks operate and theoretically have a critical eye for these things, that is what actually allows us to see things like that. Universal Creative has almost certainly taken that into account and planned accordingly within the budgets they are given. If it comes down to a choice between a painted texture on the wall, and, say, something like the fake snow and snowman down in the village, I think the snowman would be the right choice. Here is an excellent post about this very subject:
Passport to Dreams Old & New: Go Away Green
Here's a quote that I think really hits the point home: