There have been rumors about how this policy could vary from established expectations.
I've never had problems re-activating an OEM Win 7 installation at least once. If I did it twice, I might expect to escalate to the telephone number and digital voice recitation of long numerical strings.
I bought a motherboard two years ago, with an IB-K 3570 and 16GB Corsair XMS thrown in. Ironically, it was still a bargain for the motherboard, the lack of prior abuse or overclocking pretty much just short of certainty. But in swapping processors, my hand slipped, the corner of the processor jammed down on the pin-springs in the socket, and I mangled several, at one point breaking a pin while attempting to straighten it. The board was a loss; I walked away with about $200 in RAM at current reseller prices (i.e., Egg) and the processor, which also new was worth well over $250. The seller of the bundle had thrown in the OEM complete white-box for Win 7-64 Ultimate.
I replaced the board and the processor, and went through the telephone difficulty of reactivating the OS. No problem.
There are all sorts of mishaps that can occur with a computer, and there is a range of estimates to the value of data or the costs in time or money to completely reinstall an OS and software. Even good backup solutions can still cause enough trouble and time in installation.
So why would M$ impose a draconian requirement on Windows 10 "free-upgrade" if the difficulties could be counted as hardware -- whatever your real story about it? Sure, Gates is gone, but a culture has its ethics, and M$ wasn't founded by Dennis Kozlowski, Ken Lay or Bernie Madoff. You're not going to use that OS install on more than one computer at a time, anyway.
I'll be surprised if people report difficulties with this for a Win 10 upgrade to Win 7. In the meantime, I'm not sure what to do about me ol' Moms' computer. LGA775, last-issued Wolfdale, 4GB RAM, 120GB Intel Elm Crest SSD -- all in an old 1998 beige Gateway full-tower case. I worry more about the security and malware risk from flurries of Publisher Clearinghouse e-mails, health newsletters, and all sorts of spam and nonsense -- with no effort to cleaning, blocking or trusting e-mails and addresses. On a scale of Moms to Me, my brother is somewhere in-between -- less of a problem.
But that old Gigabyte m-ATX board and components just take a licking and keep on -- you know . . . As for Moms, she has everything she needs, and it is more and more "too much" for her. She doesn't want to change. So even Windows 10 with "Classic Desktop" is a bridge too far.