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.