I disagree, any interbreeding is simply due to people's ignorance, in which case even if they are labeled vastly differently they'd probably still get interbred anyways. After Herichthys carpintis and Herichthys cyanoguttatum? Ignorant people will just go 'yeah they're prolly the same thing just different whatever the hell names so let's breed them!'
There are many reasons why a fish has a specific name, and one of those reason is due to likeness to another species. Green Texas refers to their likeness to a Texas, except they're green. Hence
Green Texas. Similarly, Amphilophus sagittae looks like Amphilophus labiatum, 'cept they're basically black, hence they're called
Black Devils. Similarly for Pink Firemouths, which look similar to a Firemouth, or a Poor Man's Tropheus (coz they look like Tropheus), and so on.
The name given is the name given, and if it takes off then it takes off. And so Poor Man's Tropheus refers to Neetroplus nematopus, Pink Firemouth refers to Amphilophus longimanus, Black Devil refers to Amphilophus sagittae and Green Texas refers to Herichthys carpintis.
Plain and simple.