A cleanup (removal of frayed edges/loose bits) is 4-6 weeks, a repair is 6-8. I assume he had a repair procedure to keep the cartilage intact. Plus we know they are being super cautious. There really is no need to rush him along. He probably could have started playing in early December from a function standpoint but why not make sure its completely healed with no risk of re-injury. I like the approach they are taking.
Here's the info if anyone is interested: (You have to sign up to read all of the info.)
"Meniscus Injuries Follow-up"
https://emedicine.medscape.com/article/90661-followup
"Return to Play
Return to play after a meniscus injury is expected. The timing varies and depends on the injury, treatment, and rehabilitation protocol. In many cases, athletes can return to their sport as soon as 2-3 weeks status post arthroscopic partial meniscectomy or 6-8 weeks status post meniscal repair."