Joey Bosa ran a 4.86 40. I don't think anybody is questioning his ability to rush the passer. Pass rushers don't need to be fast, they need to be quick and be able to bend. The important numbers for rushers are their 10 yd split, 3 cone and short shuttle. Let's compare Armstrong to your pet cat Ade Aruna.
Drill .....Armstrong..... Aruna..... DE Benchmark
40..... 4.89..... 4.60.....
10..... 1.69..... 1.60.....
3C..... 7.12..... 7.53..... 7.23
20S..... 4.23..... 4.48..... 4.35
Your boy Aruna may have straight line speed, but he has no lateral agility. He can't bend and can't turn the corner. Armstrong may not have Aruna's burst, but it's good enough but he excels in the lateral agility drills, scoring well below the NFL benchmark for a quality pass rusher and amongst the top 5 at the combine. Aruna's lateral agility is downright atrocious and compares closer to an interior lineman than an edge rusher.