I agree that mentioned by you is the standard comp. But not for the freshmen. Why would you pay them so if they had not shown any potential? In 5 years at least, yes, maybe.
Regarding the last paragraph, yes, if you sit on the client flow you can sometimes get large sharps.
One vs 3 years, well, it is possible to simply "attach people to phones" and the fire the lower performers. This is described back in "Liar's Poker". This may look like a successful strategy in the firms subject to survivorship bias.
Good luck with all that, but whether this is a long-term sustainable strategy, only time can tell.
On the sell side, where the job is somewhat more systematically important, it does take time to learn the business. You used to be compensated by less volatile comp, well above the levels you mentioned for MDs, not even in the first tier US banks.
My personal opinion, quant/trader jobs that do not require 3+ years to master will be AI-ed away completely in the next 10 years.
