Kobe was a fantastic lockdown defender on players with a similar build to him. But he rarely employed that ability more than a couple times a game, especially after Shaq left. Instead, he spent of the game playing the free safety role and poaching passing lanes.
Once the Lakers became elite again, they relied on Ariza ('08 and '09 seasons) and Artest ('10-'13) to guard the other team's most dangerous swingman.
I can't think of a single playoffs where Kobe locked down an elite counterpart for a series.
Also, it's way easier to play lockdown defense when you have strong rim protectors behind you. He was up in people's faces in the Shaq era because he didn't have to worry as much about what they'd do in the lane if they got around him.
I think Kobe had elite defensive ability at his position. But he usually conserved his energy for offense. He certainly didn't deserve the 2nd half of the All-Defensive nods he got.