The short answer and the clock running behind it
A payment made by the account holder is read by the payment system as an intended instruction, so nothing about it reverses on its own. What remains is a request from the sending bank to the receiving bank, asking for whatever is left to be held. That request succeeds or fails on a single condition, which is whether a balance is still sitting in the receiving account when it arrives. Everything worth doing in the first hour exists to reach that condition sooner.
The receiving account is rarely the final destination. It usually belongs to a person recruited to pass money along, and its whole purpose is to accept a transfer and forward it within minutes. From there the sum is split across several accounts, converted into something else, or taken out at a machine. Each of those steps removes another part of the balance that a freeze might have caught.
The size of this category explains why banks keep desks dedicated to it. UK Finance counted 248,070 cases of authorised push payment fraud across 2025, with 576.4 million pounds sent by the payers themselves. Every one of those payments was approved by the person who lost the money, which turns recovery into a request passed between two institutions. The volume also means the person answering the call has handled the same situation before.