It's not just Microsoft, it's anyone who rents content to you. Had an interesting discussion with a friend a few months ago where he talked about all the content he'd bought from a well-known streaming service. I corrected him to tell him he'd rented it, not bought it. Even after multiple iterations of explanation, he still couldn't quite grasp that since it was held on someone else's servers and they could change their ToS any time they felt like it, all of his content was rented, not bought.
Silly thing was he'd actually already been burned by this service when they decided to withdraw access to content he'd paid for.
And I can't believe you're attempting to help the corporation brainwash your friend.
That is exactly what the corporations want, because it (a) puts all the power in their hands and (b) exonerates them of wrongdoing and punitive penalties for stealing the content he purchased.
YES, they can turn it off at any time. NO, that doesn't not mean that they have a unencumbered right do to so and can do so without penalty. It's corporate shills, intentional or otherwise, that convince people to give up their rights in favor of the company by not even trying to fight it.
What you should be doing is convincing your friend to push for not just reimbursement but also punitive damages for the material they already took away, as a sale had happened, and attempting to redefine a common-use term to be something completely different in the fine print of terms and conditions is something our legal system should protect us against. Go to small claims court and get a default judgement against them when they don't bother to send a lawyer, or more likely a settlement from their legal department because it's cheaper than sending a lawyer.