Sure, we can ID color morphs, but most of us cannot ID species and sometimes even genera. What about my examples of hobbyists labeling all Merulinid brains as "Favia," all monostomatous, circular Fungiids as "Fungia," or large-polyped Zoanthus as Palythoa? They are not just known as Zoanthus sp. in studies, they are identified to the species level (Zoanthus sansibaricus, kuroshio, vietnamensis, kuroshio). When you identify corals, you identify to the taxon, not trade name. Trade names serve a different purpose than species name; trade names are to identify the morph we want to buy; species contain a whole slew of different information such as care requirements, which species it can be nearby, etc. Do you have a source for that many of the corals in the hobby aren't scientifically identified?
As for your example of Cauliflower and Broccoli, that is because we selectively bred them to be that way. And we do have subspecies names for those specific Cauliflower and Broccoli, too. Common names and scientific names play different roles. Scientific names bring information about phylogeny, which can also bring with it information. For example, corals of the same genus generally can be placed together--we don't have any information about genus from common names. Corals in the same families can also share similar care requirements, such as the Lobophylliids (Lobophyllia, Micromussa, Echinophyllia, etc) usually prefering lower flow/lighting and being flashy feeders, Acroporids (Acropora, Montipora, Anacropora, etc) usually prefering higher flow and lighting, or Merulinids (Dipsastraea, Favites, Goniastrea) prefering medium flow/lighting.