I2S and PWM clock sources

[DavideRossi]

I’m trying to send I2S data from an ESP32-S3 to a MA12070P (a Class D audio amplifier with I2S digital audio input and I2C control).
The MA12070P is one of those pesky devices that requires an MCLK. As suggested by @miketeachman, I tried using PWM for this purpose, but no dice. When I probe both SCK and the PWM signal with a scope, I observe noticeable drift (the classic "running signal" effect).
It appears the internal clock sources used for I2S and PWM are not the same.
The ESP32-S3 has multiple clock sources that can be used for both peripherals (see I2S docs and LEDC (PWM) docs). Am I correct in assuming the current MicroPython implementation uses separate clock sources for I2S and PWM?