Yeah, the word "buy" in this is just one element of a broader pattern, and whilst per-se it isn't sufficient to distinguish between acquiring a thing or getting access to a thing, in these cases of mounts, armor and so on being sold in games, the entire framing wording and even store structure around it tends to lead people towards concluding that the meaning of it is for "acquiring a thing" not for "getting access to a thing", especially because in the absence of domain specific clarification (an absence I believe is entirely purposeful) people who aren't intellectual property lawyers and fully informed of the subject matter will tend to for virtual goods use the same logic to deduce the full meaning as they would for equivalent goods in other domains, specifically physical goods.

This is why also in the physical world legislation forces some kinds of business transactions with consumers to explicitly use the words "rental" or "lease" in order to make clear the nature of the transaction but might not have any such requirements for business to business transactions because businesses are assumed to have the capability to assess the full contract.