Play In Background claims it will switch to audio only mode when the screen is locked. I have it enabled.

When I have the app open and I lock the screen or swipe down from tho top of the screen to open the iOS notification center, the audio does continue playing.

When I leave the app while a stream is playing, the stream continues playing in a picture-in-picture mode. If I then lock the screen or open the iOS notification center, the playback pauses rather than switching to audio only mode and continuing.

This is especially annoying when pressing play on the lock screen fails to work because the app lost the stream connection or something like that. Then I have to enter my password, unlock the phone, switch to the Twitch app, start the stream again, and lock the phone.

This happens on iPhone 7 on iOS 14.7.1 when using Twitch app 11.5.