Is activating a tri-state toggle limited to toggling between aria-pressed=false and aria-pressed=true?

[mcking65]

The aria-pressed spec
includes the following language:

Toggle buttons require a full press-and-release cycle to change their value. Activating it once changes the value to true, and activating it another time changes the value back to false. A value of mixed means that the values of more than one item controlled by the button do not all share the same value. Examples of mixed-state buttons are described in WAI-ARIA Authoring Practices [WAI-ARIA-PRACTICES-1.1].

This text implies that activating a tri-state toggle cannot result in aria-pressed="mixed". Is this an intentional restriction?

We do not have such a limitation on the tri-state checkbox, which in some implementations, remembers the configuration of its most recent mixed state as demonstrated in the
APG tri-state checkbox example.

I do not see a reason for preventing tri-state toggles from having this mixed state activation feature of tri-state checkboxes. If there is no reason for such a limitation, I will propose alternative text.

[jnurthen]

The text "Examples of mixed-state buttons are described in WAI-ARIA Authoring Practices [WAI-ARIA-PRACTICES-1.1]." does not seem to be true and should be removed.

[jnurthen]

In windows an indeterminate toggle button has the same visual state as an unpressed toggle button
https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.primitives.togglebutton

MacOS allows a mixed state button but seems to discourage its usage
https://developer.apple.com/documentation/appkit/nsbutton?language=objc

[jnurthen]

closing as insufficient need.