The difference between "rent" and "purchase" has always been very clear: with the former you have to give it back, with the latter you own it forever. It is only very recently that this kind of steal-back has even become possible at all, as it can only be done with digital content delivery to an entirely-closed platform.
"You should assume that words have the opposite meaning and that big companies can steal from you with impunity" is a world I don't think I want to live in.
The "rent" vs "purchase" has never been different than it is now. Yes, purchase is a very deceiving word by design. The thing bringing it to the forefront is that they never were able to rip that physical product sold to you in the way they can with the digital product. That seems to have made people pay attention to the legalese that has always been there.
Many of these services offer cheaper rental options. When you go for the more expensive "buy" option, the assumption that you are actually buying it to keep should hold true.