Honestly, I don't mind being asked and took no offense or thought any was intended from it...
My apologies if it was perceived as an attempt to offend (even if so by others, not you).
My question was genuine, because I heard such an explanation several times, the last from my friend, a doctor. So it sounded like a common source.
Having said that, it appears to rely on a set of assumptions, primarily based on how vaccines work historically. What Alan and I had in mind, is a more recent quote by the perceived expert in the field, Dr. Fauci, that the vaccinated are equally likely to be infectious as the unvaccinated. I will try to find a source of that quote.
EDIT: someone even suggested these (C19 and the flu) shouldn't even be called vaccines, but rather shots, given that they do not create immunity, just reduce the symptoms. Which was quietly confirmed recently by CDC changing the very definition of a vaccine.