12 is optimal for Z perm (with any AUF), but there are shorter 2e2e cases (e.g. R2 U2 R2 U2 R2 U2 or R2 F2 R2 U2 F2 R2 F2 U2 or R U R' U' F2 L' U' L U F2) so in actual FMC solves you'd try to use 2e2e insertions instead.It would be good for FMC though, even it HTM it’s 12 moves, and 7 in STM.