That would be 100% ok for me, but I think the original idea of the "build" was for the spirit guardians damage to proc for every "on enter", not just at the start of the turn on enemies still standing in the area.
That's what I think too. However I can also imagine a situation where one party member armlocks an enemy and drags it away more slowly in order to give another party member an attack of opportunity. This would make sense to me, as the armlock may mean basically no defenses, but I think RAW it wouldn't qualify