BattyLizard6 to my knowledge the main issue with fractional GPU, is there is no real restriction on GPU memory allocation (with the exception of MIG slices, which is limited in other ways).
Basically one process/container can consume the maximum GPU ram on the allocated card (this also includes http://run.ai fractional solution, at least from what I understand).
This means that developer A can allocate memory so that developer B on the same GPU will start getting out-of-memory
(Notice in a few k8s solution you can ask for specific amount of GPU ram, but in runtime there are no actual restrictions)