Things that didn't "sell" the character to you.

[Kerr Avon]

It's called a "dramatic pause". Basically, it's meant to help build up anticipation, a little bit of suspense. It has nothing to do with the zombie's portrayal, it has to do with the director's choice. It's even used in non-zombie films too to make an emphasis. In the case you pointed out about, it emphasizes the impending doom for the characters in the stairwell.

Problem is it violated the rules of how the zombies behaved all through out the movie. Non of them behaved in a 'dramatic' way, they all just ran full bore at the first thing they could eat.

 

[CB2001]

Problem is it violated the rules of how the zombies behaved all through out the movie. Non of them behaved in a 'dramatic' way, they all just ran full bore at the first thing they could eat.

Even so, the dramatic pause created suspense, did it not? If it didn't, then it's Snyder's fault, not the zombies in the film.