My black and white M13s each have 1-piece keysets. That being said, if the 2-piece G, H, and B keys have the cutout for the trackpoint, I'd expect they were stock. I'm skeptical that there were ever any aftermarket GHB keys with trackpoint cutouts. Had I such a board I'd cherish it and use the 2-piece key design as a selling point if the board was put on the market.
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To address the OP, my M13s are indistinguishable from my normal type-Ms in typing feel and internal structure (excepting the trackpoint and dual-PS2 connectors).