player.audioTimePitchAlgorithm = .varispeed doesn't work

[nbashaw]

Describe the bug
After I initialize my player, I set player.audioTimePitchAlgorithm = .varispeed, but it doesn't work. (Really, I want Spectral, but varispeed should be really obvious and produce a chipmunk-like sound at 2x, so I'm just using that to try to reproduce the bug. It sounds like it's actually using lowQualityZeroLatency.)

I also tried subclassing AudioItem but that doesn't work either.

To Reproduce
Clone and run this repo. (The main file to look at is here.)

Expected behavior
When you tap "play" and increase the speed to 2x, it should sound like a chipmunk.

Desktop (please complete the following information):

• OS: macOS
• Version: 10.15 (Catalina)

Smartphone (please complete the following information):

• Device: iPhone 8, all iPhones in simulator
• OS: iOS
• Version 13.1.3