Cannot control the volume of voice calls on v85

Hello team,
I am developing an application related to WebRTC, and I need to control the voice call volume on Meta Quest 3 (increase, decrease, or mute completely).

Everything was fine at first, but after I updated the OS to v85.0,  when I turned the volume down to zero using the physical button, the sound on YouTube was muted, but the voice call audio was still present.

I was very surprised that even Facebook Messenger behaves the same way.
Is this a bug in the OS, or is it a new OS behavior?

I couldn't find any related information in the release notes.

Please help me.
Thank you very much.