I recall about 10 years ago helping put a rear discharge mower on a Deere CUT. Believe it was a special order deal for a Deere customer who didn't want side discharge. I'm sure it was a MMM Deere 62 or 72". They were made for ROW work and more the commercial line than the homeowner.
But the customer was very dis-satisfied with the results and coughed up the money to replace it with side discharge. That is the best that I remember the situation, mainly that the mowing job was not good with rear discharge (and the dealer had a rear discharge that was hard to sell).