Yeah, its like putting extra locks on the front door while the back door is wide open. However, most people would try the front door first.

A lot of domains have that feature btw. Gmail's specific feature is with the dots functioning as catch-all [1] (though Facebook apparently has the very same feature).

[1] http://www.slate.com/blogs/future_tense/2013/08/01/dots_in_g...