So Hoppen is correct in that 100% of guys not finishing out their eligibility is high, if the national average is 50%.
I think the caveat I put on that tweet is really important, though. 100% may jump out at you, but the five guys to focus on after Armstrong (Stanton, Bush, Darlington, O'Brien & Gebbia) were recruited by different coaches for very different schemes. I didn't include Tanner Lee because he was a transfer, and Hoppen's original stat was recruits. But he's probably worth factoring in, as you mention.
And now he's the #2 guy. He's making progress!