I know it's very easy to reverse an ACH transaction. The receiving bank (not the receiving account) is on the hook for 60 days (maybe more).
Zelle, on the other hand, will not reverse a payment if you get the phone number wrong.
At the end of the day the banks need to balance their books. So if an ACH needs to be corrected, they figure out what went wrong and hash it out with the other bank.
I’ve had unexpected deposits show up in my account and then be removed days later. Likely someone fat fingered an account number.
But the system works because all the banks have an incentive to make it work and a requirement their books individually balance.
But you’re right. Unless it’s a bank’s mistake or obvious fraud where the bank played a roll, they generally aren’t interested in reversing ACH transfers over consumer issues.