Above is a couple of pictures of SOG 1-0 Joe Walker firing a 60mm mortar from the hip. Walker was famous for his recon team ( RT California) often packing a 60mm mortar with them on their missions across the border. Being outnumbered by absurd amounts with no quick artillery support, having a mortar on hand when a 9 man team made contact with PAVN forces would have gave a decisive advantage in those first few seconds or minutes. Besides the advantage of having heavier weapons that 556 carbines and 40mm grenades, the mortar would have given the impression of a larger forces which would cause hesitation when it came to a quick assault on a small team. That hesitation would have given the SOG men an extra few seconds to beat feet and get a life saving head start to a LZ or defendable location to wait for air support and extraction.
You can see from the recoil in the second picture how serious it would have been to fire the “knee mortar” in WW2. Everyone knows the story of Marines and GIs who thought the small Japanese mortar was meant to be fired off the upper thigh.