In viral vector vaccines (AstraZeneca, Sputnik, Johnson & Johnson) the gene for the spike protein is introduced into an adenovirus. Following vaccination, the modified adenovirus will infect cells of the host, which will subsequently start to produce the spike protein

So if there is a difference in the incidence of myocarditis, it must be for a different reason.

https://pubmed.ncbi.nlm.nih.gov/34228411/