Hopefully not! Makes me wonder -- did Picasso actually paint that from life? It's hard to imagine anyone could sustain such a posture for very long.
I just bought one of these :
It's angled so that you can angle the guitar back somewhat while still maintaining decent posture. My wife's gonna make a strap that will wrap around my leg and secure with velcro so it doesn't slip. Unlike the guy in the painting, I play steel string, not Classical/Flamenco.