if the PH is down before the change ordone anytime near when the change happens, the named will not respawn.
This is incorrect. The PH will stop spawning, but the spawn cycle continues. When this happens you can kill the static spawn that spawns at the bottom of the ramp and it will also stay down.
Basically what happens is if it would have been a PH spawn, you will get no mob, if it's going to be Soulfury Embermeer he will spawn per normal. So in other words, it's kinda like the game clearing the PH spawns for you. All you gotta do is sit and wait for Soulfury Embermeer to show up.
I camped this guy for about 13 hours straight, then had the control switch in the zone and the PH's stopped spawning. Well I was doing something on my other monitor and decided to just leave my SK there and FD on the wall right next to the PH spawn point. Ended up going afk for a few hours and came back, still no spawn. About 2 hours later all the sudden Soulfury Embermeer spawns and drops my Jote. Did some quick calculations and he spawned on what would have been a 22 minute spawn time. This is why I believe the cycle continues, but the PH just doesn't spawn, but Soulfury Embermeer will if he was meant to on that spawn.