Fast movement changes the risk profile
Instant payment rails reduce waiting time, but they also reduce the window for detecting mistakes, scams, mule activity, or account takeover. Once funds move quickly, recovery becomes harder.
This is why real-time systems often depend on pre-transaction controls and post-transaction monitoring at the same time.
Good friction is targeted
The best controls are not blanket delays. They are targeted interventions based on amount, recipient history, device behavior, customer segment, and scam indicators.
A payment system that is always fast but rarely recoverable can become fragile. A system that is always slow fails its purpose.