It's not a new variant. It's just one that hasn't been explored since season 1.
In Season 1, walkers ran, they turned doorknobs and in episode 2, they even showed a walker picking up a brick and repeatedly smashing it against glass to break into the store that Rick, Andrea and the others were seeking refuge in.
I always chose to believe that it wasn't a continuity issue when they stopped including these walker characteristics, and that it was simply that walkers devolved as time went on and that's why they stopped.
Only because I find it almost painful to admit that it was likely that they just changed their minds and it didn't fit in with what they wanted at the time, which is fine I suppose.
I like the idea of re-exploring this aspect, as the world naturally evolves so why wouldn't they, but it's a bit daft bringing it up just before the end. As others have said, it's likely to be for one of the many other spin-off series they currently have or will have. But it's unlikely that I will watch any of these. Oh well, good try.