Agree with your definition of herd immunity. What I don't agree with is being held hostage by those who delay or avoid vaccination.If we're serious about herd immunity it must be ~80%. With possible varying criteria for certain age groups.
Those hoping for like 60% want it only so they can take their selfish, sorry personal OS travel plans.
We need a useful not convenient target & to hit it to be relatively safe, that is afterall the crux of the vaccination circus.
My OS plans (to visit my overseas elderly parents) are currently non-existent. I fully understand why this is the case right now when there just isn't sufficient vaccine supply - I don't like it, but I understand it. HOWEVER, when there is sufficient supply + sufficient time (2 months) post full supply, I - the overseas intended traveler - am no longer the selfish one, rather, it is those who don't want to get vaccinated when they otherwise have no valid medical reason not to be vaccinated who are the selfish. If after this time there is still less than 80% herd immunity - let those who have made the choice to remain unvaccinated take responsibility for the consequences of their decisions.