Not sure what the big issue here is.
Other industries have required flu vax for years. Not a new concept.
Seems the vast majority of employees don't take issue with it and the concept is in line with airlines and governments across the globe.
Regarding this being a change of view on a/c transmission, I'm not sure that's what this is.
It's a recognition that in order to permit entry to other countries going forward (if the drawbridge ever comes down) and to prevent crews isolating/quarantining on return, vax is the ticket that's needed.
Plus it would be nice to one day leave a hotel on a slip again. Can't see other governments letting you roam around on a slip without a vax.
To be fair to Alan, he makes a solid point when he says that if COVID vax is not your thing, then international aviation going forward is probably not for you.