orientation_play is a tag in which you can catalogate images were a character is not being faithful to its real orientation. Mainly viable for images were you can assimilate that the plot is giving you information about how a hetero character is having sex with their own gender or how a gay character is having sex with the opposite gender.
Even if it depends of cannonical information in some cases, I think it could be helpful for certain users. I don't consider it very likely to be mistagged. Just use this tag when you see a character not being faithful to their real orientation, people is gonna use this tag in searching bar and see the pleasing results.
In defense, I could say that this is the only tag capable of filling that context. Other tag combinations can't give you satisfactory results.