Why wasn't William Anderson in "Magical Mystery Cure" "Pinkie Pride" and "Hearth's Warming Tail"?

[StaryStory 4,264]

William Anderson is the background score composer for 97% of the FiM TV series, but from these three episodes for some reason he's absent, Daniel Ingram is the one who composed the BGMs for them instead

At first I thought it could be because these are musical episodes, they feature a bunch of songs so it would naturally make sense for Ingram to compose the BGMs for them due to his bigger participation, but other episodes with a lot of songs such as "A Friend in Deed" and "Crusaders of the Lost Mark" have William Anderson credited as the BGM composer, so...?

[FirePuppy 739]

I could tell you why, but I'm not ever exposing leaked production content on this forum.