Re: Isn't this normal?
I think you may be off base here. A man trap, as I've seen them, fits multiple people, but won't allow both doors to open at one time, so that in order to unlock the inner door, you have to close the outer door. Thus, if you fail the hand print / pass code / key card authentication, both doors lock, and you're stuck until the authorities get there.
The goal is to slow people down, so nobody can get in or out of a secure location without plenty of time to be observed by security, and to catch absolutely everyone that attempts to enter without permission.
And yes, as far as I've seen, most high end (expensive) data centers have these. I've heard it was to make them able to host certain types of government servers, but who knows how accurate that is. Either way, it's not really a unique or notable feature.