Let me first say that Eddie Bravo's jiu-jitsu is amazing. It is second to none. This is not a bash on Eddie but more of a warning to NOT listen to his advice on flexibility. Eddie is what we would categorize as hypermobile....... Think of the far opposite of being really tight and stiff. Like BJ Penn, he is genetically like this. Following Eddie's advice may be the quickest way to see a knee surgeon. At minute 3:30 of the video he states that you not only need flexible hips but you also need flexible knees. Yes we need good hip mobility but our knees are meant to be a stable joint. Stretching the ligaments in your knees makes as much sense as having a training partner kick you in the zipper in order to callus up your groin.
This is why most people who try to play a rubber guard end up with severe knee problems.