yeah well everything can be learned, i guess - the question was, why didnt it catch on, and i guess the answer is, the solution that almost every frame has today, vertical dropout inside the rear triangle, does the exact same thing as the Klein one, but allows for easier wheel change and possibly more variation on the dropout shape itself.
Also the Klein variant seems to put the rear axle in a different position in relation to the RD hanger eyelet (right?) this might mess with the RD geometry,