The "Academy Lt." who was her instructor in Advanced Tactical Training was never formally identified as Chakotay. This was the original idea, but they decided against it on Voyager when dealing with Chakotay's backstory. The actual name of the instructor was never mentioned on screen. Chakotay's stated date of resignation on Voyager is a couple of years before Ro would have been at the Academy, anyway
They actually do --- Episode: "Preemptive Strike" right at the 8:47 mark on my video they mention "Lt Cmdr Chakotay" where Ro goes on to say "A man I both respect and admire...".
You must have a different version than I do, then. I just pulled that episode up on Netflix. Her exact words:
"I'v heard a lot about the Maquis. One of my instructors at Tactical Training, a Lieutenant Commander in Starfleet, a man I both admired and respected, he was sympathetic to them. He resigned and left to join them."