This is unfortunately no longer that accurate. It's still a good basic guideline, but there appears to now be a random element to each PE spawn, either moving it up or back by a few minutes. PEs also usually don't spawn if only one player is in that local instance, but they sometimes also won't spawn if many players are there. I'm not saying don't use this, I still do use it myself - but expect it to be wrong a fair amount of the time.