Bendix and K/H were both suppliers at the time, it is not uncommon to see a mix, usually front to back and not side to side.
An interesting detail is that like you saw, the hardware should match the backing plate to be correct. Also, I have found the rubber plug for the adjustment access holes to have the big numbers molded in for Bendix and smooth or a cross-hatch pattern for K/H. Probably details very few have paid attention to.