Zombie Pigmen Aggro After Killing Ghast

A connected player was complaining that the Pigmen were attacking him even after they had go rid of all the aggressive Pigmen. They left the nether to go work on other projects. Upon returning to the nether, they were greeted with several aggressive Pigmen. I told them to pillar up at least three blocks, and wait for me to assist. I got rid of all the Pigmen in a 50ish block radius. They spotted several more on some elevated terrain, so I switched to creative flew up there, switched back to survival and waited to see if they would attack me, the Pigmen did not. So I let the other player know it was safe to get down. They earned the Return To Sender achievement, but doing so caused the Pigmen to attack the player again. I died in an attempt to assist them fend off Pigmen, which is unfortunate, but the only solution for that player was to switch to creative mode, and switch back to survival (which I still do not fully understand why that worked).

With the other player disconnected, I went to the nether, attacked a zombie Pigmen, let myself fall into lava, and went back to the nether (to see if I could reproduce the issue). The Pigmen were still highly aggressive and attacked me on sight. I left the nether to finish filling out this report.

Upon further reading, [Mod] Urielsalis said "Zombie pigmen are meant to stay hostile for 20 to 39.95 seconds". So I went back to the nether, after spending several minutes writing this report, and checked to see if the Pigmen were still aggressive, they were, and upon pillaring up 3 blocks, and waiting well over a minute, they were still aggressive. Eventually a ghast spawned, shot me down and the Pigmen killed me.

A few things I am unsure about:
1) I am not sure why switching gamemodes seemed to fix the Pigmen aggression issue
2) I am not sure why Pigmen would turn aggressive when another mob was being attacked / attacking the player.
3) I am not sure why Pigmen would "remember" an aggressive stance when the person who attacked them either killed off everyone in the vicinity, or left the nether, or had the proper cooling off period.

Could be related to:
MC-148600 - Seems to be the original
MC-69715
MC-100202
REALMS-1746
MC-64337
MC-98380
MCPE-27646

I feel that the mechanics for the Pigmen aggression is a bit wonky, and has some unintended behaviors.