Or I could be wrong. But the main takeaway is that for a while he was also looking progressively chubbier (partly due to water retention I guess). I'd say he's gained a fair bit of fat along the way, and there's no way around that. He'll probably start cutting soon. Looking at his face on this photo (December 14th), maybe he already has:
If that's the case he won't be able to put on much more muscle than he already has at this point.
EDIT: @ArmsHeldOut yeah, that photo illustrates the point about him probably already cutting even better.
Anyway, In my book, if this is more or less his final size, that means a slightly physically underwhelming Batman.