Duly noted and agree. Since I never use one finger chords it has never been an issue for me, but I believe that if they use a simple system, it should at least be on a musically-correct basis, not "add a black note to the left" to get such-and-such.
The "other guys" use a C for a C chord, add a flatted third, Eb, for a minor and a Bb for a seventh. At least you could progress musically with this as a start.
DonM