I don't expect him to produce evidence, but I expect him to say more than "I suspect he cheated"
If he saw something unusual, like "Hans was messing with his shoe" or "I heard several vibrations coming from Hans during the game" etc.. that would be at least something.
Magnus has produced what he can given the situation and has staked something of extreme personal value—his legendary near-2900 ELO—on it with his move-1 resignation.
If he'd heard the guy's damn shoe buzzing he would have insisted on a search.
If he saw something unusual, like "Hans was messing with his shoe" or "I heard several vibrations coming from Hans during the game" etc.. that would be at least something.
It would be something. Magnus has given nothing.