If you want me to tackle the calc itself with the assumption that Queen really is headbutting at lightspeed;
We don't see any reactions from Queen here; there is no sign that he intentionally stopped his own movement the very instant that he struck Sanji.
And it does seem extremely weird for an
FTL+ Sanji (who you'd expect would have reactions that fast too, right?)
to be hit by a lightspeed attack that he can plainly see coming at him. Sanji can move over twelve times faster than Queen, but couldn't move a couple meters out of the way while Queen's head was travelling 6+ meters towards him?