I would say it’s typical, if not normal. What you’re probably experiencing is a high amount of tension being focused in those areas because of the stiffness in the system. In order to get a stretching sensation, or maybe even just to get into the position for the stretch, you have to put a significant amount of strain through that anterior musculature and the associated tissues.

Kelly actually did an interesting pro episode a while back about using the couch mob as a diagnostic for mobility issues in the front of the hip and leg. It can give you some insight on where in the system you’re really locked up, and therefore where you can target some soft tissue work (balls, foam roller). If you’re experiencing that much discomfort (not to mention numbness), I would just use small doses (15-30sec) of the stretch interspersed with soft-tissue work for the front of the hip, thigh, and/or shin meat. Use the couch mob as your “test/retest” to see how much working on one of those areas improves your position.

As you soften up those stiff tissues, you might (and hopefully will) find that the couch mob becomes more comfortable and accessible for you.