How to get an AudioStreamPlaybackPolyphonic's stream's playback position?

Godot Version

4.4.1 stable

Question

I’m trying to use AudioStreamPlaybackPolyphonic for cross-fading different background music but it seems that the class does not have any method for getting a specific stream’s playback positition. The AudioStreamPlayer2D’s get_playback_position() returns 0, and so does the AudioStreamPlaybackPolyphonic’s method of the same name that it inherits from AudioStreamPlayback. Do I have to create timers that call lambdas in order to bypass this issue? Or am I missing something? Should I make a feature request on github?