I would think all ability stats grow with each amount of EXP you gain, as with all other sailors, but a small percentage of not much is not much.
e.g my Kaiser B.O with proper experts and vets only gives 6 repair 0 overheat at lvl 120, I'm sure it was probably +8 or +9 base stat for repair.
This figure would be even more miserable with stripped B.O's for SS etc (obviously)
At the end of the day i don't think its that much to even be considered given a decent Repair Man.
Just my opinion, someone with greater knowledge may be able to enlighten us further.