Username field briefly displays "Sign in" when entering Play mode

How to reproduce:

1. Create an empty project and open it
2. Enter Play mode
3. Observe the result in the top-left corner of the Unity editor

Actual result: The username field flickers with “Sign in” before reverting to the signed-in user’s name
Expected result: The username field keeps displaying the signed-in user’s name

Reproducible with: 6000.3.0a2, 6000.3.23f1, 6000.5.10f1, 6000.6.0b10, 6000.7.0a5
Not reproducible with: 6000.0.82f1, 6000.3.0a1

Reproducible on: Windows 11 Enterprise (25H2)
Not reproducible on: No other environments tested