As far as I know, neither an S-video connector nor a set of component connections has a pin that will allow you to detect whether the signal is anamorphic or not.

S-video connectors are simply chrominance and luminance separated into two pairs of pins (ground and signal for each).

Component is simply Luminance (Y) Chrominance Red (Pr) and Chrominance Blue (Pb), with Chrominance green derived as a subtraction operation from the Pr and Pb channels.