Test Environment:
OS Build: Windows 11
Version: 24H2 (OS Build 25346.1001)
Browser: Edge dev
Browser Version 114.0.1807.5 (Official build) dev (64-bit)
URL: https://mgt.dev/?path=/story/editor--editor
User ID: V-id
Screen Reader: Narrator

Repro Steps:

1. Open the above URL and login with valid credentials.
2. Press 'Ctrl+Win+Enter' keys to turn on Narrator.
3. 'Microsoft Graph Toolkit Playground' Overview page will get displayed.
4. Press tab key and navigate to 'Mgt-Planner control and press enter key to activate it.
5. Now press tab key and navigate to the docs option and press enter key to expand it.
6. Press tab key and navigate to the 'Assigned to me' button and observe the issue.

Actual Result:
Screen Reader is not announcing the state information as 'Collapsed' while navigating on the 'Assigned to me' button.

Expected Result:
While navigating on the 'Assigned to me' button then screen reader should announce the state information of the control and it should announce the information as 'Assigned to me button collapsed.'

Note:
Same issue is repro throughout the application for the same control.
Same issue is repro with NVDA.

User Impact:
It will impact the screen reader user as they will not be able to know that whether the control is in expanded state or collapsed state if the screen reader will not announce the state information of the control.

WCAG Reference:
https://www.w3.org/WAI/WCAG21/Understanding/info-and-relationships

Have feedback to share on Bugs? please tag bug as “A11yRCA” and add your feedback in the comment section.