Not 100% sure but reading that email, the purple pads read like they could be an SPK pad, made by ProjectMu to the specs of HC+. Possibly not a ProjectMu branded HC+ pad like the green ones in the picture.

Only guessing here and trying to decipher the bullshit from my armchair.

Edit: Also, reading it again. The email from SPK says "The HD by SPK Japan brake pads are manufactured by PMU." It then says "The green colour pads are HC+ spec and was an interim colour before we (presumably SPK) specified them in purple"

I don't know enough about brake pads or these companies, but, the wording here could mean some (the HD) are manufactured by PMU. It doesn't necessarily say that the HC+ purple pads were in fact manufactured by PMU.

Not meaning to fuel any fires but the wording isn't 100% clear to the layperson in my opinion.

__________________
Bush chook enthusiast