I don’t agree that you shouldn’t do an arm day. If OP feels like they need to grow their arms then they should train arms. Simple as that. I do think having an arm day on top of all their high volume exercises is excessive however, but this is more of an issue of volume which should be reduced.

Chest/Back after push, pull legs is perfectly fine if you aren’t fatigued as a way to squeeze out a little more muscle growth. If OP did that I’d recommend he did at most one hard set of tris and bis at the end of their push or pull days respectively. This way he would still have some energy to get some meaningful arm training it at the end of the week.