For a kid that played safety in HS, moving from EDGE to ILB is probably less of an Adjustment to play in space.
It's still a concern, no doubt, to pick a player at 15 whose production came in a different role at a lower level of competition. Especially in a draft rich with safe 1st round defensive talent.
I'm good with Reddick at 15, even above Foster, but not without hesitation. And, if above Foster, I'd assume it's for non-football or injury concerns.