I summitted last week. We came up from Guitar Lake, dropped our packs at the trail junction, and proceeded to Whitney. My wife advised me to carry my permit and I joked "Ya, sure...like there's going to be a Ranger up there." Actually we saw two. But neither asked to see our permit. One seemed to be collecting wag bags.
A couple of years ago I unexpectedly encountered a Ranger on the Mountaineers Route. He asked me if I had a permit, bear canister, and wag bag. I replied yes, yes, yes. He took my word and I did not open my pack.