From those photos (and he could look completely different irl), he has filled out nicely and got a lovely gloss to his coat but still has room for plenty of muscle development. I'd not worry at this stage about topline but concentrate on getting his bum nicely muscled up, topline will follow, when he's working correctly from behind.
he has already come a long way in a few months - look at the difference in his chest!
You can def see an improvement in his bum. The neck is a little fuller, but main difference that I can see is him bottom is much rounder/fuller. Very good start