why would this door be here?

[MacIronhawk]

Notice that building. It's also on Cuba, and that door can be accessed as a back entrance.

It's just the model. Because you can't see the back of the building, Disney didn't really need to bother with taking the door away from the model, just because the inside only has a one way door.

That's all it is. What would be interesting is if you could go into the building through there, now that'd be a big mistake on their end.(since there's only one door on the inside)