about VOC resonant match

There is anther problem, the picture show above is a vco,and he said that reflection coefficient is -45°
while the s11 is 45°,it resonant.
but in my view,the im(Zin) should be equal to im(Zs),
and in this case,the im(Zin)=2.375, im(stoz(s11))=7.8. it not equal. why?