Multi-course ouds and lutes of course predate anything resembling the modern guitar by a long, long way. Do you consider those in the “guitar family”? If so, I’d refer to the group as oud or lute family. Guitar family is a recent subset of lute family, and doesn’t even contain the first multi-course instruments.

https://en.wikipedia.org/wiki/Category:Guitar_family_instrum...

https://en.wikipedia.org/wiki/History_of_lute-family_instrum...

>almost as old as guitar-family instruments.

They are as old as we can trace it back, vihuela/viola de mano were multi-course, as was the baroque guitar which developed from them. The romantic guitar brought us single string courses and in the guitar family double courses died out other than in a few nooks and crannies. I don't think this has any effect on what TFA proposes and the author is well aware of this bit of information, but it has been years since I read it and maybe I am forgetting something?

agreed - America went through a "mandolin mania" in ~1880s, and even in the 1900s and 1910s, the guitar was by no means an established instrument.

As a matter of fact, the "tenor guitar" was made for people who knew how to play the very popular four string banjo, but wanted to play a guitar without learning new chords.

Instruments were in a state of change, and the "harp" nomenclature (and styling) for a 12-string guitar was more a marketing flourish than a family lineage.