SMAL is the only multiplication insn that requires DATA64 RS1

[marcfedorow]

Actually SMAL rs1, rs1, rs2 is equal to SMALBT rs1, rs2, rs2.
I am not sure that non-destructive SMAL has any critical purpose.
Not adding SMAL to ISA may simplify (already pretty large) P-ext multiplication logic.
I think that removing SMAL is a suggestion consistent with RISC-V approach (in terms of reduced ISA).