So what is MM referring to here,
"“Great kid, hard-working, very powerful,” McCarthy said. “But there were just a lot of things, when he does them, they’re for the first time. Hopefully we’re out of that phase of his development. I look for Jeff to take that next step. He made the step in your second year that you look for. He did it first on special teams.”
What are these things that he's been doing for the first time, break dancing? Maybe badminton? How about lawn bowling?
It's called player progression for a reason. Aaron Rodgers was critiqued by some fans for a lack of appreciable progress in his first seasons started. But the stats didn't reveal that AR went from pretty much only throwing to one side of the field at a time, lots of flood plays, and scripted plays to becoming a real veteran signal caller with increasing pre-snap responsibilities.
The critiques of Janis' practices last year focused on other parts of his game. That's new and exotic mistakes, as RR pithily refers to them suggests that the Coaches are giving him more to work with. This isn't a new and mysterious concept.