I think it is probably much ado about nothing. The league usually wins the grievances. At the same time, if the Sixers accepted that Ben was having mental health issues he should have been paid. So that's where it would get juicy, actually having to litigate that. Seems like it would have been easier to stick with the back strain (but really, same issue: team doctors say he's healthy enough to play, player and his own people say he isn't).
At worst I think it gets quietly settled, especially if Ben did in fact get 50% of his salary before the season even started (reports seem to vary there). Contractually, was that written as an advance on future services that have to be delivered or is it more of a bonus/balloon payment? Is he supposed to give it back to cover the fines?
Either way, I seriously doubt an arbitrator is going to find anything that calls the Sixers and league's right to to fine him into question.