I'd say it's as good of a theory as anything else. I've kind of figured if the variants change enough, that this is how you can get covid twice. It's been pretty rare from my understanding, but this is likely how it happens.
I'm not a doctor, but I read that myocarditis most of the time gets better on its own over time. If that's the case, then I'm not sure what the huge concern is. I'd love to see the data on long term issues from the vaccines such as myocarditis or blood clots, but I'm guessing the reality is there is going to be a very very tiny sliver of % who suffer from such long term issues (or death) which would make it safer than a natural infection which also can bring on long term issues (or death).
Isn't myocarditis potentially dangerous under extreme exertion, like say playing sports?