If you read the mitigation efforts segment on the wikipedia article for female body builders
https://en.wikipedia.org/wiki/Female_bodybuilding#Policies
It is reported that it is estimated that 80% of professional female bodybuilders get breast implants so they can maintain upper to lower body symmetry, because of the reduction of body fat that comes with the sport, and the need to keep up with an image of femininity
In that sense
@ArashiRen Yamato is quite gifted to avoid the cruelty of physics, for she would have to get under the scalpel in order to compete, this also means of course, that breast implants are a legal operation for competitive body builders, which i didn't knew before checking, so in that world it doesn't matters if the competitors are all natty in that regard