That's exactly it. I don't think he's trying to 'do the voice'. His voice is very quiet, and he doesn't make his wording as dramatic as Heath did. I think that's deliberate. This is HIS take on Heath's Joker. He's not trying to be Heath's Joker. He's paying homage.
But like you Pennyworth, the thing which struck me more than anything were the storylines and the production, plus the acting is very good. The scripts are very original, and he's taken it to a broader scope outside of the TDK world now, which is good. It's more than just an impersonation - it's more like a mini-movie.