So here's what the article glossed over, and I do understand: the "legal right" to record a cover song, in the United States, involves contacting the rights holder of the composition / publishing rights. For most popular songs, past and present, that has been the Harry Fox Agency (only recently has Loudr joined the picture).
HFA required, at the time of my asking, a blanket amount. For the granting of the "legal right" to record the cover, HFA had an introductory tier of X,XXX units. As in, to record one digital copy of the song, the up-front payment was the equivalent of it being sold in hard copy (or digitally) X,XXX times.
X,XXX multiplied by the royalty set by law is not an insignificant sum. For an independent artist, non-label backed or advanced, this amount is prohibitive. Thus, either go the legal and potentially costly up-front route, which is real and was glossed over in the article, or go the unlicensed route.
What your comment fails to address in the latter part, regarding remixes, is that according to press releases and public information by SoundCloud and Dubset, "rights holders" are granting a negotiated statutory right for the providers to host and provide compensation for the use of someone else's recording. Your statement is correct in the legal, traditional sense, but that statement is apparently being revised through market forces, as noted in the article.