It’s a good view right now in this instance, and although historic what is the concrete effect of him joining a picket line? He can easily still be working against the ultimate goals of the unions. Though the backlash if he took obvious action against the unions could be much worse now that he has been seen in such a way. But yeah, we shouldn’t be too critical because it is still above what most politicians do in regards to unions.
I agree with the comment currently below mine not to let this sort of gesture diffuse the drive for deeper changes.