This issue is driving me bonkers as well!
I can’t seem to find a work around. It’s clearly a battle between Apple and Adobe/black magic though. Someone is not willing to budge somewhere to let them talk to eachother properly. (Fast money is on apple being stubborn)
I’ve been able to work around this by simply finishing it Resolve.. great.. happy days. But now, just like the OP, I have a job where the client are providing logo files etc and i’m going from AE to FCPX (animating the logo and importing the .mov back to FCPX to finish the video) and there is the blasted gamma shift issue. It seems FCPX’s import is using the same settings as quicktime and decides to change the gamma for whatever reason. ANNOYING!
There used to be plug ins and solves in FCP 7.