YouTube ran an experiment with up to 4x playback on mobile (???) but it went away in February. I get a lot of the experiments they do being experiments but why just allowing the slider to go farther is such a back and forth hoopla is beyond me. It's one of the oft touted features of 3rd party apps and extensions with nearly 0 UI impact to those who don't want to use it (just don't slide the slider past 2x if you don't want past 2x).

https://www.theverge.com/news/603581/youtube-premium-experim...

As a premium subscriber I currently have 4x available on Android and they recently (in the last month) added it to web too

As a premium subscriber I no longer have 4x available on iOS and I never had it on web. I also no longer see it as an experiment on https://www.youtube.com/new

I hope they make up their mind on it soon instead of this endless A/B testing.

Probably, because they are "A/B testing" things, that do not really show much effect or depend on more circumstances, than they care to eliminate and then overinterpret the results. Like almost all corporate A/B testing.

Install this: https://mybrowseraddon.com/video-speed-control.html

I listen to a lot of videos on 3 or even 4x.

I have up to 4x (in steps of 0.05) with YouTube Premium on Android

Meanwhile, I've found that just reading the transcript is often good enough.