Changing theme's "Default Base Scale" does not change anything

Godot Version

v4.3.stable.flathub [77dcf97d8]

Question

When i change the “Default Theme Scale” in the project options, this also scales texts accordingly. But when i set “Default Base Scale” of a Theme, nothing happens.

I would like to set this value on runtime. And i would like to see the same behavior like the project setting has. Theme.set_default_base_scale(2.0) or ThemeDB.set_fallback_base_scale(2.0) both don’t help.

Changing the Theme’s “Default Font Size” does work, so it can’t be an issue with the place i put the Theme in.

What am i doing wrong here?