This isn't entirely correct, as we obviously have pet bar and custom UIs on Blue. The real answer is that although technically they are
not classic, they were
close enough to classic, and people were so used to having them here (after over a decade), that Rogean "grandfathered" them into classic.
Notably he didn't do this with some similar stuff, like say DoT tick damage messages, because they weren't close enough in the timeline.
Only custom UI/pet windows were grandfathered, because they were added immediately after classic.
As for when Green will get them ... no one knows for sure, but my money is "whenever Green characters merge into Blue"
[You must be logged in to view images. Log in or Register.] But who knows, maybe there will be a brief period at the end of Green's life where they'll get them.