Anybody see other rationale for this advice of moving bitcoin to a new wallet?
I haven't head such a recommendation from anyone reliable. Perhaps I just don't understand what you are trying to say?
(As an example, one of the places I have read this is in a "trust no one" three-step security strategy recommended by dacoinminster here.)
Link please?
I've read this a couple of places as a security step, forwarding your loot on to new wallets. The example referring to three steps articulated in this "trust no one" post regarding maximum security is here:
https://bitcointalk.org/index.php?topic=33835.0 -- scroll down to the summary three steps.