Oh, I see. Since putting a plain sound ID from playsound in there works I had mistakenly assumed that was the format. Thank you for clarifying!
This definitely describes a bug.
I think this is a bug. If it worked properly it would work more like player heads' note_block_sound component which accepts any sound event rather than just vanilla ones. Please check again.
You can also see this bug with only one salmon, bucketing it and placing it down repeatedly and observing as its size randomly changes.
Can confirm in 1.21.
If I were a PVPer I would probably just avoid 15-block-tall towers.
This still occurs in 1.21.4. They're affected by lighting, if you put fireworks down two tubes of tinted glass, you'll see that one in a tube that is lit on the inside displays brighter that an unlit tube, even on the outside of the tube where the lighting is the same. This is odd for a light flash, that you'd not expect to act like fog.