I would vote you up if I had modpoints today.
The upgrades from the full systems pop up whether the useraccount is linked to the microsoft account or if you simply created a user on Windows 7.
And yes, if someone signs up specifically for a beta program were every click is analyzed and any feedback linked to an account I think it is OK to get the free copy connected to that account. Because this copy is free (as in beer, but not as in speech).
It does not upgrade a bought copy. The alternative would be that every installation of the beta gets a free copy, even if the user did not participate in the beta program.
I hated MS for diversifying the directx-bases because every new directx was only available if the user bought the newest windows. They nearly destroyed the pc as a gaming machine in order to push their xbox. They were evil in general and their monopolistic behaviour was illegal. They tried to kill Linux by FUD.
The free copy is the right thing to do to atone for the abomination that was windows 8 or even 8.1 (two different userinterfaces for account settings, nuff said). And a free copy for every one who beta tested seems fair. Even non genuine windows installs get the upgrade, but there will be nagging.
I don't see much change in their behaviour myself. Could be wrong but way it looks to me is free isn't a usable experience liked genuine (business) customers will get. Testing is going to be the suckers who buy into it and updates forced on those users with MS stating after months of testing on home versions it will be rolled out on the real customers machines. Months makes it sound liek they are releasing it with barely any testing done inhouse. Way to make people work for free, not sure that is how it will work but my gut says maybe