A lot of the big dudes getting beat by the small guys was in pass situations, and I think Robinson and Koht can likely play that type of role just fine. Quickness and leverage can absolutely help a smaller guy be successful in that respect.
There's a big difference in how much smaller we're talking about though. Guys like Anderson, Braswell, and Turner were way smaller than then OTs they faced, but were big enough to still hold up in the run game.
Then there is smaller like where Robinson and Koht are: Robinson is 231, Koht is 232. Roster weight for Braswell was 255, Turner 252 and Anderson 253. 20-25 pounds of good mass and muscle makes a HUGE difference in the ability to get into and hold the gap, especially when it's edge contain. At UW (scheme we are moving to), the "small edge"/Wolf guys on the 2 deep were 255 and 260 so still a bigger body type than what Robinson and Koht are.
They remind me of an early Tim Williams, who was a great pass rusher the minute he stepped on campus and was able to contribute in that role but didn't get expanded responsibilities till his last year when he finally got up to about 245. Even then he was never the full time guy as that was Ryan Anderson as Anderson was able to hold up on the edge (being bigger/stronger) better than Williams could