Why doesn't volume adjust on individual songs work on iPhone or iPad?

Even with Sound Check on, I have several songs that are significantly louder or softer than other songs. I've tried turning Sound Check OFF on all of my devices and adjusting the individual song volume on my MacBook, and it works, but ONLY on my MacBook - the volume remains the same on my iPhone and iPad. I've tried changing Uploaded, Matched, and Purchased songs. I've tried clicking Update iCloud Library on my MacBook, and then rebooting my iPhone - still doesn't work. I CAN update start and stop times, album artwork, lyrics, etc., and the changes take effect immediately on my iPhone. Why does volume adjust not work??

I don't know how to tell what version on Apple Music I'm on, but I'm on iOS 18.2, and assume my Apple Music is the latest version as of 1/1/25.