I find "m=m" used in nfet_20v0, nfet_20v0_* (5 varieties iso, nvt, nvt_iso, reverse_iso, and zvt), nfet_g5v0d16v0, pfet_g5v0d16v0, and pfet_20v0. All extended-drain devices. Another weirdness of the PDK is that there is an "nvt" device and a "zvt" device. They are both the same device. There are minor differences in the layout.