I agree, though I don't think "instincts" is the best term. It's more ability to read/diagnose what's happening in a split-second. A 5.0 guy with top diagnostic ability will get to the ball faster than a 4.5 guy without that ability. Spence is a perfect example. Of course the ideal is a 4.5 guy with elite skills at reading the play.
That's the problem with trying to convert DEs. Ability to read the play is something a kid develops well before they arrive at a college. By the time a kid is 19 yo it's usually too late. Sort of like trying to learn to hit a fastball at age 19 (well maybe not that impossible). Better to take guys who actually play LB (or Safety).
As far as Jackson, I'd be happy if he committed, but I do have some concerns about his actual LB skills.