This study is, actually, irrelevant to disproving the claim above.
It checks for the myocarditis infection from COVID-19, but it doesn't actually control for vaccination status. The people studied either are believed to have been COVID-19 infected, or had been vaccinated, but there was no designated unvaccinated control group.
In which case, you are potentially using "breakthrough cases" of COVID-19 causing Myocarditis to make your point (assuming they would be the same pre- and post- vaccination), rather than a definitive look at people who did not get the vaccine and how they fared. All the study proves is that COVID-19 infections cause increased Myocarditis... in vaccinated people. If you assume that COVID-19 has the same Myocarditis effect in vaccinated and unvaccinated people, it works; but if you accept that maybe the effects of COVID-19 are different in vaccinated people, it could fall apart, which is why the study about how Myocarditis doesn't seem to effect the 160,000+ unvaccinated people studied still has value.
Risk of myocarditis following infection before vaccination was 11.14 [95% CI, 8.64–14.36] greater than the risk of vaccination, and risk of myocarditis following infection after vaccination was 5.97 [95% CI, 4.54–7.87] greater than the vaccination itself.
It checks for the myocarditis infection from COVID-19, but it doesn't actually control for vaccination status. The people studied either are believed to have been COVID-19 infected, or had been vaccinated, but there was no designated unvaccinated control group.
In which case, you are potentially using "breakthrough cases" of COVID-19 causing Myocarditis to make your point (assuming they would be the same pre- and post- vaccination), rather than a definitive look at people who did not get the vaccine and how they fared. All the study proves is that COVID-19 infections cause increased Myocarditis... in vaccinated people. If you assume that COVID-19 has the same Myocarditis effect in vaccinated and unvaccinated people, it works; but if you accept that maybe the effects of COVID-19 are different in vaccinated people, it could fall apart, which is why the study about how Myocarditis doesn't seem to effect the 160,000+ unvaccinated people studied still has value.