The stance typically referred to as "goat-clamping stance" in Wing Chun is Yee Jee Kim Yeung Ma, typically translated as "two character abduction horse stance". The "two character" refers to its resemblence to the character for two in Chinese. "Abduction" refers to the drawing in of the knees which apocryphally is similar to clamping a goat between your knees so as to, I dunno, sheer it or something. The "Ma" at the end means horse in Cantonese, but can generically be said to mean "stance" in the same way that "Kuen" (Fist) can generically be said to mean "martial arts style".
There is a similar turning in of the knees in Seisan Dachi/Hangetsu Dachi. Notably, however, the feet are staggered, rather than parallel as in Yee Jee Kim Yeung Ma. Also, from the picture, the weight seems to be in the balls of the feet rather than in the heels. Although different schools of Wing Chun may teach differently, it is traditional that the weight be in the heels for ease of turning from Yee Jee Kim Yeung Ma to Chum Kiu Ma facing either left or right.
No, they are not the same stance.
