I'm the guy who loses if it's a shuck, so show me it's worth my money. I bet not. I can be shown a reasonable stand of proof. There's a sucker born every minute, folks, just like P.T. Barnum said. And a fool and his money are soon parted.
Musicians do fine without it.
I hear songs on the radio and know what the chords are as I, II, V, etc, but not the key it's in. I hear the fifth, rooth, third, etc, in a riff, but not the actual notes. I don't see where anyone needs this course, even if it works.