There's a bit more nuance here than merely Citi wants to reverse a wire transaction. The article explains they were servicing debt and accidentally paid the loan off early (rough summary). The debtors could argue they had no reason to suspect error and viewed the payment as settling the loan.

New payments contracts now include "revlon clawback" clause. The blockchain analogy is a buggy smart contract that gets fixed.

The article explains why.

They asked the Hedge Fund to transfer the money back. Citi is a bank but couldn't reverse this mistaken transaction and had to go to court.

If this was done by check, Citi could have simply cancelled the check.