Update... My connectivity issue is still unsolved, but I did a nuke & pave in connection with another issue and learned that Apple apparently pulled the bad (silent) update before I was ever aware of it.
After a clean installation of OS X 10.11.3 I did not have the entry in System Information that's been mentioned, /System/Library/Extensions/AppleKextExcludeList.kext is at v 3.27, not 3.28.1 or 3.28.2, and I've got no pending software updates.
Confusion cleared up, anyhow.
