LB is the hardest position to project (on defense) mainly because you can't measure intangibles and intelligence at a camp. You also have a lot of kids who don't even play off-ball LB (like Henderson). His whole tape is on the edge.
This is why we see so many low ranked LB's turn into All Pros. Traits are important for LB's but after a certain point it's just diminishing returns. You don't need to be 6'3" running a 4.4 to be a great LB. A guy who's 6'0" running a 4.6 but studies film relentlessly and plays violent can be just as (if not more) productive.
At the end of the day, even if we recruit an off-ball Linebacker there's a really good chance that Hetherman is gonna have to start from square one with the kid once he gets on campus. Most high school coaches aren't teaching Linebackers to do what we are.
I've had this discussion with Hetherman and other college LB coaches multiple times. The new LB's often arrive with a basic "see ball, get ball" mentality, they don't play with their hands and they're often overly aggressive to a fault. (i.e. they just run straight into the line of scrimmage recklessly)
The way we play LB has to be taught from square one...so we recruit athletic, long, violent kids and mold them. (and hope they figure it out)
It's literally the same thing I've had to do in high school when I get transfers.