I agree it could be a useful tag, but we need to make sure it is used in the right way. There is a high risk that it gets the same problem as the penetration test tag - it is used for question about anything, that just happend to arise while the poster was working on a bug bounty.
To combat that we need good and clear usage guidance, preferably that explicitly explains how to use the tag and not just what the words mean. Maybe something like this (just a suggestion, I am sure it can be improved):
Use for question about the design and workings of bug bounty programs. Do not use for questions about bugs in general, or for questions that is not explicitly about the program itself.
But still, in my humble opinion it would be a useful tag, so I say create it!