I don't see why addons should need to be able to cancel auras/buffs.
What's troublesome is that the green posts linked on the wow forum don't seem very clear as to whether buff addons will still be able to present right-click-to-cancel functionality for auras/buffs gained in combat. Or maybe it is clear - I don't know much about secure button templates or whatever.
You wondered why they now use CancelUnitAura instead of CancelPlayerAura. Well, I think it has to do with the new vehicles since they also use PlayerFrame.unit. So most likely there will be a change in the unit you control when using a vehicle I think.
Vehicles are considered pets, yea. The default UI swaps the player and pet units on the frames. If you use a UF addons, the vehicle shows up as your pet. So it makes sense that if you're in a vehicle and can cancel special buffs, you're not cancelling them from you, but rather from your pet.
What's troublesome is that the green posts linked on the wow forum don't seem very clear as to whether buff addons will still be able to present right-click-to-cancel functionality for auras/buffs gained in combat. Or maybe it is clear - I don't know much about secure button templates or whatever.
There's no "need" but don't tell me the salvation removers for tanks are not convenient (or in any way overpowered)