Firefox in private mode have not become the same as the theme

[munmigenui]

OS：Ubuntu 22.04.5LTS
FIrefox version：131.0.3 64bit

The maximize, minimize, and close options of Firefox in private mode have not become the same as the theme,

but in Firefox normal mode.they are the same as the theme.

For my Chrome browser, whether it is normal mode or privacy mode, the three options in the upper right corner can be displayed normally and the same as the theme.

In addition, the maximize, minimize, and close options in the upper right corner of my extension client are also not displayed as the theme, but the system default icons.