That preprint you linked estimates a rate per million of 561 for myocarditis, for young adult males. OP's preprint show a rate per million of 537 for young adu

That preprint you linked estimates a rate per million of 561 for myocarditis, for young adult males. OP's preprint show a rate per million of 537 for young adult males on their second dose. I would say the research definitely isn't conclusive yet. For young adults, whether the vaccine is safer than getting COVID is an open question, but we do know the absolute risk for both (vaccination or getting COVID) is small.