The difference is in one pixel.
The BIG difference is the length-heigth ration, that determins the looks of the gun. The mount appears from distance as somewhat tall box sitting top of cone...or half of it. Despite its top is curved, the curving takes place in so top of the turret, that the 15 cm scale doesen't allow it to be presented without over-exaggeration, which in place would ruin its looks, making it look like a half-ball, which it is not, only from 1/3 part of the the very end.
Now, if we drawn the turret in 11 pixels, we need to realise that the entire heigth of the system in SB is also 11 Pixels, thus we get to square shape, and that flattens the looks dramatically. Naturally, if we follow the overexaggeration, we could risen the system as well, but then we have considerably larger object in terms of its real size, and onboard the drawings, it starts to look.
So thus the art of exaggeration can also work as art of
underexaggeration which is to minimizise the shape, in order it to fit more into the clumsy pixel-vs-pixel presentation, that is hell for everything round.
This, as results of tons of references, drawings from both Soviet/Russian and as well from Finnish construction plans and 6 years of Shipbucket drawing evolution.
And besides, like I said, I have no objection of others using what ever version they want in their own drawings. I just know what version I'm going to use in mine.