So this is a good point. I was just talking with a colleague about this. Some of the herd immunity models take factors like how mobile people are into account. It seems like masks could be a factor in the models of herd immunity. This might be a semantic argument. If population characteristics such as age are part of herd immunity (which is a moving target depending on population), then mask wearing could be considered a population characteristic and included in the model. This would net "drop" herd immunity levels.
The distinction comes down to factors that change (behaviors, mandates, regulations, etc.) and those that don't (age, gender, etc.).
Saying we've reached herd immunity given behavioral changes is largely meaningless, as most people do not want to continue these behavioral changes indefinitely. One of the biggest changes that you failed to acknowledge is that people are not in contact with nearly as many people in their day to day life as they were before. Working from home, kids not in school, limited social interactions, etc.
It's not herd immunity if a return to previous behaviors negates the immunity.
What's going to be interesting is: after coronavirus is over and we're down to non pandemic levels of infections in the states, restrictions are lifted, and people start going about their pre-pandemic business, I wonder what the explanation will be as to why there's a permanent immunity.
How long will people continue to flog the 'people are continuing to be responsible' horse?
What will it take to finally accept that there's a physiological immunity taking place giving herd immunity?
Behavior is a variable that can and should be included in a herd immunity model. The percent immunity needed to achieve Herd immunity will change with behavior. That doesn't negate that it's happening. Louisiana and Florida are pretty much open and seeing a drop in cases. Bars aren't open indoors- but I think we can live with that for a little while?
