Again comparing apples to oranges and I think you missed the point.
Boulware was a top 200 player, solid 4star, he wasnt a walk on. And he did those stats as a Senior, comparing him to a freshman Flagg is unfair. The point OP I think (albeit maybe doing a poor job of explaining) is Boulware ran a 4.9 and was not fast. Flagg likely runs close to a 4.9. Boulware racked up all those stats you mentioned yet went undrafted, signed with the panthers after the draft and was released before season started, then signed with the 49ers practice squads and was released 7 days later and since then has been out of the NFL. i.e. you dont need to be an NFL lb-er to play at a high level in college.
You can win a championship with average LB play if you have ELITE dline play, that clemson Dline is what OP is underselling, that thing was stacked and allowed him to get those #s. By his senior year, he did have good instincts. Is it truly a stretch to say Flagg could post those numbers in 4 years with a dline like clemsons? Boulware had 20 and 40 tackles his first two years.