Shown values don't make any sense. 10uF would represent about 0.8 ohm capacitive reactance at 20kHz, while series resonance of 1mH and 10uF would be at 1.5kHz
Class D amplifiers have very little phase shift
Too many diagrams to post here, so I just blogged it:
https://inatinear.blogspot.com/2020/02/class-d-amplifiers-do-not-have-horrible.html
The 20 degrees at 2 kHz argument is bunk.
https://inatinear.blogspot.com/2020/02/class-d-amplifiers-do-not-have-horrible.html
The 20 degrees at 2 kHz argument is bunk.