In the logout screen we use activeFocus to determin which action will be triggered.
Here you only have those buttons as controls, tabbing essentially changing it, so having an underline for focus isn't needed and clutters the layout since the opacity already changes depending on your selection.

Underline was added by D9431 but shouldn't be in logout.
If we want to have an underline we really should only have it with focusReason Tab but that would require QQC2 Control as base instead of Item