Maybe I've just never noticed this before (don't think so), or maybe it's something new (don't think so), but this week Clyde Baum and Robby Taylor have U21 team advertisements on their player page. As to why they just appeared now I am not sure. Taylor popped this week but Baum didn't.
Neither is good enough to play on the team, obviously, but still kinda neat. If both were a year younger, I would be confident that they could be on the U21 next year (except for Taylor's Star Potential). They are well rounded basketball machines, as evidenced by the fact that they have been starting at PG/SG all season and I'm 11-4.