I turned on the subtitles and when I wrote this command:
"/playsound minecraft:entity.wolf.howl voice @p"
the sound played correctly but did not display in the subtitles.
I am sure that it is more than this sound it does not display the subtitles for.
I have found these:
-entity.wolf.howl
-block.glass.fall
Linked issues
Comments 2
duplicate of MC-91893, mentioning your findings as well
These sounds aren't implemented yet (AFAIK), so they don't have a need for them to have subtitles. It still would be nice though!