I think your last paragraph sounds about right. The Max is a compromise on battery life for those who want the absolute most possible performance, but I think Apple is seeing a much wider audience get the Pro chip. Anecdotally, whenever I see a tech person mention their Apple silicon device, it's almost always a Pro chip. I'm sure only a small fraction of that user base is hitting all cores with a full load on a regular basis, but a majority are certainly enjoying a killer battery life.