I am not the OP but I thought this was interesting and wanted to chime in.
Personally I don't consider them zombies in WWZ, but that's due to a personal definition of what a zombie is. While a zombie doesn't have to be slow, it helps so much to build the idea of a constantly chasing threat that will catch you if you stop moving. Always having to watch your back and being worried about getting overwhelmed is far more thrilling than running zombies, which don't give you a moments rest to think about it.
However the main reason why I don't consider them zombies in WWZ is because they aren't actually trying to eat you, they are trying to infect you. A single bite and they move on. The fear and horror of being eaten alive, before slowing becoming one of them is terrifying. The fear of getting a single bite and turning a few seconds later, not so much. They've lost any real distinction at this point and they may as well just be murderers who happen to bite you instead of stab you with a knife, or whatever.
While technically they are undead and they spread infection through biting, it takes more than that for me to personally consider them a zombie, or more importantly a monster. The difference between the 28 Days Later and WWZ zombies is almost nothing, yet one is just a feral human being and the other is undead. Put them side by side and they are exactly the same.
This is just a personal opinion on what zombies are though. I am bias in that I love the old school shambling zombies that are easy to avoid but could become a serious danger if you slip up. I always found that far more frightening than simply a monster that's basically just a human gone feral. I actually didn't mind the zombies in the Dawn of the Dead remake so much because the infection was slow and the zombies themselves actually ate you alive. There were also only a few cases where the speed of the zombies mattered and the film was more about them being trapped inside, rather than having to escape them.
I don't mind WWZ referring to them as zombies and I accept they are zombies on a technical level, but I don't consider them a conventional zombie.