I've searched for the Yellowtail Parrot fish for a few hours now and it seems not to spawn. All other 21 of the 22 unique tropical fish spawn except for this one. This also seems to be an issue for all bedrock, because I found a few other tickets for other platforms that had been closed due to the users not responding.

How to reproduce 

Start a creative world, use command: "/summon tropicalfish ~ ~ ~ minecraft:become_yellow_tail_parrot"

A white cod will spawn instead.
I tested this with other of the 22 fish (ex. yellow_tang) and they spawned correctly. The white cod seems to be a result of any incorrect fish because I also intentionally spelled the name wrong as well as trying every variation of yellowtail parrot I could think of.