Just an update of sorts.
This work in code version 16.1r4 and earlier it appears. But not in 17.1. In 17.1 it builds the dhcp snooping table but doesn't ever see the client renewing/rebinding and so the table entry expires briefly while the client renews its leaser (if it can). You never see the table state as renewing or binding.
Works beautifully in earlier versions though.