There is the slight difference that Sigurd was able to essentially land in a half press-up position, which would be incredibly unwise with a normal arm, but his left arm could take it. 

Gigue's weight is significant, but he has to contend with both Sigurd's natural strength and his supernatural magic super-arm, which is more than capable of lifting Gigue's entire weight alone, twice over. Super-strength is interesting in grappling situations (this is something I discovered in the Kanitah vs Fury fight) because in human battles gravity gives the advantage to the person on top, but when characters have superhuman strength the advantage actually shifts somewhat because the person on the bottom can actually use their strength to push off and the like. 

Point being, even if Gigue did sandwich himself on top of Sigurd's body for some reason (because I'd presume he would rather be in a back-mount, with his chest up) the elbow slamming into his side could force him off Sigurd's body unless he was ready for it.