I think it's a grey area and most such reseller offers probably do skirt the edges of their licensing agreements with Microsoft.
On a different, but related topic. I am now party to two different class action lawsuits against AI companies for downloading books from pirated online libraries. Basically, the online pirates stole the books (mostly as PDFs) and offered them free or at minimal cost. The AI companies took advantage of those huge libraries to train their AIs. So, in essence, OpenAI, Meta, xAI, Perplexity and Anthropic re-stole stolen copyrighted materials. Two of the books I authored or co-authored are in those libraries and subject to compensation, should any materialize at the end of the lawsuits.
I don't expect more than a couple hundred dollars when all is said and done, if that much. The attorneys are going to do well though.
The point is that the internet has long been a wild, wild west for bad actors. Just because you can find great deals out there doesn't mean they're legit deals.