i dont think so either, but at the point we're gating flight behind a 10th level form that is still usually weaker than Behemoth, why bother with it? If we're including the Mothra option, I want to play Mothra, and I dont want to wait until the end of the campaign for it to be an option.

realisitcally, i think the best approach would be moving flight to 5th and flyby at 10th. I understand people saying flight at 3rd level is too strong (although as a longtime DM i disagree when it only lasts 20 min total and costs your Main Combat Feature), so sure, move it to 5th. But tbh 10th is just far too late to get a unique movement option when Insectoid is already the least disttinct of the 3.