Summary:
On Windows, the Narrator screen reader incorrectly reads a focused TabButton as having 'Selected' state, even when it is not selected.

Repro: 

1. Create a TabBar with TabButtons as follows:

TabBar {
  TabButton

{     text: qsTr("Home")   }

  TabButton

{     text: qsTr("Discover")   }

  TabButton

{     text: qsTr("Activity")   }

}

2. Start the Narrator screen reader on Windows.

3. Use the Tab key to tab to the TabBar. Then use the Left and Right Arrow keys to change focus between the Tabs. The screen reader will read the name of the TabButton along with  'Selected' even for TabButtons that are not selected. Note that to select a TabButton, the Space key or clicking must be used.

Expected:

The screen reader should read 'Selected' only for TabButtons that are actually selected, such as those have been selected by clicking or by pressing the Space key. Currently, it looks like the TabButton is incorrectly providing the 'Selected' state when it gains focus. (Focus is different from Selection for a TabButton.)

This bug does not repro on Android and macOS, so it looks like a Windows-specific issue.