...according to MA, they were in the Academy together from 2353 to 2357
That indeed comes from "Conundrum" Okudagrams, which the blu-raying process ought to make fully legible to the discerning audience (and never mind that it may still require freeze-framing, which is "cheating" of sorts, just like reading the Okudagrams through backstage sources would be).
FWIW, the "Conundrum" files seem to establish that everybody spent exactly four years at the Academy, which is different from what our TOS heroes experienced. Supposedly, even brilliant students could not shave a year from their studies, and nobody did a fifth year. (Well, Wesley might have, had he ever graduated.)
Maybe something similar to Picard's incident on Stargazer - taking command when the CO and XO were out of commission - allowed Riker to rise so rapidly. His talents for command were probably recognized early.
Or then it's simply that Captain Pressman made sure that Ensign Riker would become Lieutenant Riker ASAP, and in all that hurry would conveniently forget what he and Pressman had recently been through.