I would guess it's because we've faced some damn good TE's and slot receivers the past couple months. ET is too small for the TE coverage role, but completely agree that he can cover more ground in coverage. With respect to the blitzing aspect, I don't know if I've ever seen Kam with a sack (?) but do often see him in run support in the backfield or at the first level. Your OP is an interesting observation and I wonder if there's a pattern associated with it.