50% and lower rate (the hk children myocarditis study) isn't a "much lower rate". Factor in omnicron and the clear difference between vaccinating everyone and 10% of society getting the virus and unsolvable questions should begin to arise.
In reality, even if you get Omicron now it's so mild it's unlikely to cause any more heart damage than any other common cold. The danger has passed. Except that, almost everyone decided to massively expose themselves to spike protein over and over. So if spikes cause heart damage and they do, especially when the vaccine gets into the bloodstream, then the vaccines will do more damage than the virus could ever do simply because nobody has pre-existing immunity to it.
https://www.ijidonline.com/article/S1201-9712(21)00571-3/ful...
Many patients who are exposed to SARS-CoV-2 quickly fight off the infection with an innate immune response before the adaptive immune response really engages. That can happen with no pre-existing immunity. Some people just have better immune systems.
https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd...