WPF AutomationProperties.LiveSetting="Polite" not triggering live region updates

### Description

I have an AccessText element with text that updates every second. I hope that each text update doesn't interrupt the previous reading by Narrator. However, when I set the property AutomationProperties.LiveSetting = "Polite", it still doesn't work. Narrator still interrupts the previous reading and starts reading the next text update. the version of dotnet framwork is 4.8

### Reproduction Steps

1. Add an AccessText that updates once every second, and set the property AutomationProperties.LiveSetting = "Polite".
2. Turn on Narrator scan mode.
3. Use the arrow keys to make Narrator focus on the AccessText.

### Expected behavior

The expected result is that after setting the AutomationProperties.LiveSetting = "Polite" property, Narrator should not interrupt the previous text reading, just like the aria - live="polite" property in HTML.

### Actual behavior

Narrator interrupts the previous reading and starts reading the newly updated text even before finishing the previous one.

### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

_No response_

### Configuration

_No response_

### Other information

_No response_