Which I've had failed as a student in Australia, as we use .edu.au (not for Dropbox, but other services).
As you said though, its a simple test, and if you don't think about it too much, its too easy to just test the email ends in .edu and move onto the next task.
Sure, if you go for international markets you have a lot more work to do. But in most countries you cant use extension to verify anything. I had a .edu as a university student in denmark, but I think my dapartment was the only danish education instituion who had that, the rest just used normal .dk domains.
As you said though, its a simple test, and if you don't think about it too much, its too easy to just test the email ends in .edu and move onto the next task.