Take a look at this pic:
https://forums.macrumors.com/posts/5398407/
The fan blades aren't shielded from above, and the bottom case is a little bit flexible (actually when you take it off you notice how thin and floppy it really is). So I think beatsme is correct.
If you're not paranoid about your warranty, you could open up the case carefully to see if there's anything in the way. If you do it carefully, they'd never know you'd been in there, even if you are super paranoid!
Once you remove the screw, the bottom just comes right off (i.e. there are no connectors or anything you have to worry about). It's pretty easy really.