Simple - some rules are more relevant than others. Like here on Getbig. I take racism, malicious bashing, and other issue more than some others. Same with the IFBB. Jumping and competing in another federation is the number one violation. What you do on your own time is something different. You either promote the IFBB or not. Whether you and I like that issue is mute, you don't need to join the IFBB, it is on a yearly basis whether you renew it or not.
Bodybuilding has NO rules ron, it is total chaos. "Athletes" are allowed to do whatever they wish (including severe drug abuse, spousal violence etc.. etc.. etc...)
The "RULE" that athletes can not compete in any league they wish is just an invention by the weiders to protect their dwindling empire.