An acquaintance lives outside, in an empty lot far enough away from people who live inside that he hasn't been run off by the cops yet.

He connects to the Internet via Cricket, a cell-phone type ISP. Because of his remote location it's slow. He sent me a message yesterday in which he reported that he couldn't get a decent connection, even if he walked to the top of a local hill, line-of-sight with a cell tower. Then he upgraded to Windoze 10, which went very fast, but after re-booting after the upgrade his connection went back to slow.

My best guess is either that Microsoft subsidizes bandwidth for the upgrade or someone else upgraded just before that and it was in a cache.

Anybody know? Have another hypothesis?

Windows 10 uses a p2p type download that can drastically increase the speed downloading. And once upgraded, will automatically share(steal) your available bandwidth (only when "idle") in order to make the download faster for others, as well, unless you specifically turn it off.

See this?