I think its actually more realistic :P
If you think about it, if you put the bottom brick on our top it would just slide off because of that border :P
If you think about it, the whole design of the brick stud wouldn't work, as the tapering bumps would have no friction against the bottom of another brick. The reason lego studs work is the friction from the 90º sides onto the 90º sides on the bottom holds them together.
