This crap is why I dislike advanced statistics as they're discussed in basketball.
Advanced statistics should break basketball players down into their many complexities. How does this player perform in this position, this role, this set, this situation. I suspect that's what real analysts, employed in front offices, are doing. Instead all these public-facing stats seem to do is attempt to boil players down into a single number or talking point, and that's just not very useful at evaluating how good a player really is. It's very good, however, at getting attention like this - which is where it makes its money to begin with.
I don't know how JB measures out in front offices. I suspect there was a reason that the Celtics, reputedly an analytics-forward organization, gave him such a massive-usage role last season despite his poor metrics. I also suspect there are good reasons we can't find a taker for him at our price right now. As it is, I'm content to settle this with him like professionals before the start of next season, go to battle with him as we've done for the last decade including several deep playoff runs and a parade, and reevaluate the landscape as necessary from there. There's no "leverage". We get what we're looking for or we keep the second team all-NBA guy.