How can this be legal?

That's not what it says. Virginia is the one that defines over 80 as reckless per se. But in VA, reckless is a lesser offense than in DC, which has a higher standard but also has harsher penalties when that standard is met.

The problem is the reciprocality. DC is considering the VA reckless offense to be the same as a DC reckless offense - and suspending the license. But they aren't the same offense.

(Its almost impossible to do 84 on the interstate in DC. There's very little interstate in DC anyway).

when I was in the military and lived in Virginia and worked at 8th and I, I would use my motorcycle on the HOV lane and hit 3 digits quite frequently. Made the ride in much easier. I don't think I would ever do that now, I was only 21 then and I know it was irresponsible of me to ride like that.