The bug

There is a bug in which the idle sound of husks and zombie villager, and their baby variants, is overlaid with a regular zombie's version of the same sound.

How to reproduce

/playsound minecraft:entity.husk.ambient hostile @s
/playsound minecraft:entity.zombie_villager.ambient hostile @s

It appears that say3.ogg is the only one affected out of the 3 possible ambient sounds, so this issue only occurs about 1/3 of the time. It does not affect drowned (only husks, zombie villagers and their baby versions).

See also: video posted in comments, showing this issue occurring with a baby zombie.