Overnight, the update offer to 10240 happened, all set on that VM.
Fired up another 10162 VM today, no go, no offer of 10240.
So perhaps Microsoft is sticking with nighttime downloads only, to avoid Akamai CDN abuse during the day, perhaps. Just a theory.
I wrote something up about how you can see which CDN your upgrade comes from at https://TinkerTry.com/download-windows-10