I guess that explains why B is also heavier
Yeah, me too.
Btw, all B modules are exactly +60% heavier than A or C modules.
Edit :
Which, to follow up @Rankaze post up there, make them quite cumbersome (well, it ruins your jumprange) to use on Condas. On everything, I guess, but yeah, Condas have exposed PP, and B8 are heavy

I used to rock one, but recently chose to downgrade it to A7.
As I see it, the game in its current form is SO brutal when you lose your shield, that accounting for "post-shield" play is just... stupid, basically. I'm talking about Conda, here. Smaller/faster ships can probably get some distance and wait for their shields to recharge, or outmanoeuvre their enemy. Condas can not really do that.
Ofc, having a B module would be better in theory, but... you never want to lose your shield ever, because bulkheads do nothing to protect modules, hull reinforcement do nothing in that regard either, and your PP and thrusters are so very exposed in a Conda, it's simply not worth it. Just put everything on shield, and never lose it. Or run before you lose it.
So in the end, yes, having B module for PP and thrusters (B7 thrusters really
feel heavy, though) would be a nice idea, on paper. Same with bulkheads (hull reinforcement would be bad, either way). But,
imo, it's actually a bad idea, in the current state of the game. Just go with shield, and make sure your never lose it, ever.
Btw, I really hate this current "everything for shield" meta. I find it very boring. But Conda sure can go crazy, with shield boosters and SCB. So might as well just do that, spare your weigh, don't bother with "B armored whatever" modules, don't even bother with bulkhead (nor hull reinforcement, for god sake), and
pwn faces. Sigh.