[JohnR34231]

I see two odd characterizations:

1. Referring to Chryst and Burns as "Rookies" is spot-off.

2. Dylan Jackson is not in the mold of Chase Thomas or Trent Murphy.  He's a DE, not an OLB.

What he means of course is that Chryst and Burns will be new to the starting roles, in other words inexperienced.
You are certainly right that the usual definition of rookie is someone new to the program, not to a starting position.

As far as Jackson is concerned, I think he means tall and rangy, rather than referring to specific position.

[JohnR34231]

I see two odd characterizations:

1. Referring to Chryst and Burns as "Rookies" is spot-off.

2. Dylan Jackson is not in the mold of Chase Thomas or Trent Murphy.  He's a DE, not an OLB.

What he means of course is that Chryst and Burns will be new to the starting roles, in other words inexperienced.
You are certainly right that the usual definition of rookie is someone new to the program, not to a starting position.

As far as Jackson is concerned, I think he means tall and rangy, rather than referring to specific position.