The age and sex disparity in post-vac myocarditis would seem to disqualify that hypothesis. It's not like young men have veins in their deltoids where other demographics don't.
Tasting saline after an IV injection in nonsensical.
Tasting saline after an IV injection in nonsensical.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2806387/
EDIT: Young people, specifically men are also more likely to get myocarditis in the general population irregardless
What makes you think the percentage of inter-vascular injections causing myocarditis should be distributed evenly across a population?