I somewhat agree.. but its also become somewhat of a fad to say this. Weak players are still getting pushed aside.. strong defenders are still getting called fewer fouls because they don't have to lean in as much..Everyone always thinks that big/strong PGs are better to have on the defensive end. This was true when teams would exploit a mismatch against a small PG and take him into the post. This rarely happens anymore. We all know that almost everyone runs their offense through PnRs now. This is where a small/quick PG can sometimes be to your advantage as they can use their size (lack thereof) and quickness to evade the pick and stay with there guy better than a large PG who will almost always get stuck on the pick. I'm not saying that I'd rather have a Larkinesque type guy as my starting PG, but at least for our backup I would approve of him.
And Larkin, though a superb athlete, hasn't shown he has an explosive first step.. sans a couple highlight reels. Even in college he got moved off defending the scorer on the perimeter for a lack of being able to defend as well as his teammate Durand.