I mean yeah he can, but the the topic was about being a perfect counter to law. Law is a smart characer and sanji still gets ragdolled even if an attack has no effect, see egghead, so imagine if it was an actual fight Law would go for vital points and knock him out in rapid succession, like TAC said, kill him twice.
But like i said maybe im overselling law
I just mentioned the laser example to illustrate just that this ability is not fixed, it clearly progresses with sanji, not that are neccesarly more deadly in that context