As others here have pointed out, Cisco reserves the right to do this but doesn't do it in practice. They don't even have a realistic chance to _detect_ a Cisco-programmed FS SFP, since it simply identifies the same as a genuine Cisco module.
If your case was directly related to the SFP (“I can't get a link on this fiber port”), then yes, they could probably refuse it. But if your case is about basically anything else on the switch, they won't care.