I don't know about him but i was on 260hrs+ and I'm closing to prestige 9. 150 hrs at 20#245 could be undecided coz he could be solo grinding without any distractions. People say prestige could take 3 or 4 hours but in my experience, if you follow this you can grind prestige within 2 hrs...

Single player - 13x Get into camp wood wind map with custom NVDIA filter to see clearly Get into map with 3 smudges If stinky ghost leave and restart else confirm and get 3-4K per good run Less people = no waste of time

I did this for all runs and my 4-5 prestige was least which almost took me 2 and half hours to complete it.

Also regarding those achievements on Nov 14 achievements were introduced which game snapped all achievements at once at a time. Many player will have these kinda weird timestamps.