Have seen similar clips. Many can take groin shots and keep coming, an untrained person not tough or trained in anything then yes a punch to the stomach or kick to the groin may drop him. Here is somebody tough (sadly now passed away), you really think with someone like him a kick to the groin would have dropped him or a poke in the eye stopped him? You'd just make him more angry!
Tommy Carruther's 'dryland swimming' drills may be his idea of realistic training but they aren't to many others, none of his students look very good at all and would be in for a very rude awakening against a good street fighter or an experienced MMA fighter. Put protective gear on spar all out full contact see how many groin kicks or finger jabs you can land, with someone good at closing distance and takedowns you will probably get the chance for a single kick or kick and one punch, or kick and finger jab before getting taken down. With 'dryland swimming' drills going back and forth or dancing around you can land anything often, in all out full contact sparring it is totally different. The groin is a small area and to hit were it hurts against a moving target is very hard, as is finger jabbing and landing to eyes with a moving live target. When you spar all out full contact you find out also how much energy certain techniques take and that no matter how fit you are you cannot sustain them, try Straight Blasting all out hitting as hard and fast as you can against multiple opponents (or multiple people holding focus mitts) for a mere 30 seconds then see how you feel. Real fights should be short but can be longer or in mass brawl situation if you cannot simply walk away.