Press Gaggle by Scott McClellan
MR. McCLELLAN: I just don't have anything to update you on, but things are moving forward, and the Saudis are cooperating and working to make that happen.
It's wrong to delete on, isn't it?
If McClellan had said: "I don't have any need to update you," then "on" wouldn't make any sense.
But there's something (or nothing) to "be updated on" in the sentence as given, so it wouldn't work without the "on."
The expressions are:
"to update someone or somethng"
"to update someone ON something"