Majority of performance is reached on 4 physical cores while increasing to 6 starts to show some minor scaling in some BfA spots.
https://rk.edu.pl/en/analyzing-world-warcraft-multi-core-scaling/
Addons and more so other applications running in the background may increase the amount of cores needed to not get a performance hit. HT helps a bit on low core count situations but when you have enough physical cores it’s not really useful (some “game modes” even disable it so that the game doesn’t end up using logic cores on same physical cores).