Because I don't really get your argument here. How would Sanji hurt Nusjuro, and how would it be enough compared to other supposed Power of Love users like Kuma who couldn't do anything to Saturn and Gaban + Xebec who also couldn't do anything permanent to regen merchants?
Although, Garling at least comments on his wounds needing a long time to heal. Nusjuro just calmly ignores the kick and bites Sanji.
I don't even know where the second head stuff comes from as I don't recall it being part of the Yokai powers he has either