In ACH, they generally happen together, and with at least a few hours of delay. That's why instant generally usually doesn't use it.
In ACH, as soon as you get the notification about an inbound credit transfer, it's effectively final. Whether it ultimately settles on the same day or 1-2 days later is irrelevant, since what matters is finality.
ACH credit transfer clawbacks are very rare compared to ACH debit rejections (due to e.g. insufficient funds or fraud).