I think he's not a dispassionate observer of WFH trends. Lies have an underlying motive, and he's shown before that he is willing to lie in high-stakes testimony to avoid a negative outcome. Dimon's WFH assertion was made to analysts, and in his role as a leader at JPMorgan, presumably for a positive motive (market sentiment, boost morale, ensure a return to normalcy). This wasn't an off-the-cuff observation. By equally likely I mean he was in a situation with a clear motivation so the likelihoods are between truth and falsehood. In that frame, 50% is generous.

Edit: the above does preclude the idea that "truth" can have a motive behind it as well, but I don't particularly think he deserves the benefit of the doubt.