The Bug

The powered rail or activator rail updating sequence is reverse of that of earlier versions. More specifically, while rails in 1.18(or earlier) update in a sequence opposite of its sequence of being powered, they now update in the same order as that of its powered order. A more vivid description of this change can be seen in this video Minecraft News: 22w11a Mangrove Roots Are Insane - YouTube by ilmango, starting from 20:10.

Steps to Reproduce

This is easy.

1. Build a chain of observers with its 'face' facing upward and 'power' downward.
2. Place a series of powered rail (or, alternatively, activator rail but with same type throughout) 
3. Place some power indicators (like redstone lamps) underneath each observer.
4. Use a power source to power the rails, and observe the lamps.

Redstone Lamps may not be as conspicuous. It's recommended to use an item conveyor chain consisting of droppers with comparators as indicators.

The behavior should be different across versions.

This bug has devastative impact on many old redstone mechanisms that rely on the update sequence of rails. If the change is unintentional, please fix it.