This is true and if it was flu kind of virus with very low reproduction number, it would be right but Delta variant has very high reproduction number and it is

This is true and if it was flu kind of virus with very low reproduction number, it would be right but Delta variant has very high reproduction number and it is guaranteed to infect eventually almost everyone who is without immune response against it. There is also this fact that myocarditis has high prevalence among teenage boys (even CDC might underestimate it) and it looks like it is caused by some form of immune reaction and its occurrence is immune reaction size dependent (Moderna causes more myocarditis than Pfizer that causes more than AstraZeneca). It allows to postulate that it might be that the people who get myocarditis after vaccination have high risk of getting it after infection.