Not really related to this suggestion at all. Better to start your own thread if you want anyone to notice your idea.
I would ease up on the newer posters. We don't need to be the forum police.
Give dwarves castes because why not?
You're encountering an example of
jargon, a case in which a group of people with a specific interest (
e.g., Dwarf Fortress fans) develop their own vocabulary to discuss that interest. This can include coining entirely new words, or repurposing existing words to have a new meaning. In DF context, the word "caste" has been altered in just this way: It no longer means a part of a stratified or diversified social structure (well, it
could, but currently does not), and instead basically means "biological sex". See
here.
But for future reference, "why not?" isn't a persuasive argument. Toady and Threetoe are busy dudes, and a suggestion that reads like "Pour hundreds of hours of work into this radically society-altering idea that I've put zero design effort into, because, why not?" is unlikely to generate a positive response. If you really want to see dwarves of different social castes become a thing, take Shonai_Dweller's advice and start a new thread about it. But
first, flesh out a detailed framework of what you'd like to see, what
other people might like to see, and how the game might feasibly create procedurally-generated variations of all possible examples.
Convince Toady & Threetoe that your idea would improve the game, for the majority of players, and do what you can to make your suggestion easy for them to implement.