I would assume that if user A grants everyone in the world a license to do X, Y, and Z, then you're allowed to submit your work to company Q which requires you to agree to terms that say "YOU give us permission to do X, Y, and Z". Even though the permission is technically not yours to give.

Because, logically, if you did interpret it this way, what could possibly happen that anyone could sue for? If you grant company Q the right to do X, Y, and Z and company Q actually does one of those things, user A can't claim they were wronged, because they granted the whole world the right to do X, Y and Z anyway.

I think technically, you would be in violation of their terms of service, but it wouldn't cause any problems so no-one is likely to care. It only takes one person to have more money than sense for you to end up in court, though.