I believe you and the OP are talking past each other. The OP didn't reference R value, just herd immunity. Take the US... Certain sub-populations could very

I believe you and the OP are talking past each other. The OP didn't reference R value, just herd immunity. Take the US... Certain sub-populations could very well have herd immunity within that group. A group like meat-packing plant employees and their families. They've all had COVID or been vaccinated. But, within the group of "white collar workers who can afford to remain socially distant", we could be a long way from herd immunity - this group has remained distant (low number of past infections) and hasn't been eligible for vaccination (<65 years old, mostly healthy). Yes, at a macro level, herd immunity is mostly binary. But, over a population of 300,000,000, there's a lot of room for sub-populations with differing levels of immunity.