Tropical fish and pufferfish don't spawn in lukewarm ocean

Expected:

Tropical fish and pufferfish spawn in (deep or not) lukewarm oceans, like java.

What happens:

Tropical fish and pufferfish don't spawn in any lukewarm oceans, unlike java. Also, salmon spawn here too, which isn't right either.

Why is this an issue:

Well if you want to get a ton of tropical fish for a collection or breeding axolotls, you have to go to a warm ocean which is kind of rare.