I don't think the specific way they are trying to define it makes sense but I will say that the idea of a solo dev is.... Misused a lot.

Most games (especially on consoles) even with "solo devs" are the work of a bunch of contractors on top of it. https://twitter.com/waypoint/status/1263221231945465858

Their argument is the same as "musicians who use samples, are they real musicians?" Which.... I don't care about that dead horse argument. (They are).

I would be much more interested in discussing the idea of solo devs and contractors that get left out of the conversation

The idea that only some are important enough to be part of "development". Do solo devs mean they designed everything? Made the art? Programmed it? Only the "core team" that's attached to the studio name?

Would the development of the game have been possible without the concept artist they paid for a pitch deck? The marketing person helping with copy and media? The QA team that provided feedback and bugs? What about platform support provided? Is there some minimum work needed?

This is also a problem with small teams and large teams sometimes too, not just the mythical "solo dev" where the success/development of the game is attributed to the main developer/studio, but rarely ever to the small army of contractors that helped along the way