The reason being you can train the same movement in a resisted situation. Without having to kick people in the groin.
a perfectly reasonable way to gain timing and power with a technique is to train it against a resisted opponent. This is difficult with a groin kick as very few people will get kicked in the groin on purpose. So to gain the timing and power needed we can use an existing kick and change the angle a bit.
this kick is effective to the inner leg anyway. The set ups are the same. The openings are the same. If you can reach the inner leg. You can reach the groin.
kicking to the leg will provide a real reaction that you can work the rest of your combinations off.
i prefer this to relying solely on pads or compliant drills.
I kind of think you're conflating a few different issues here.
First: the
type of kick to use for targeting the groin. If your opponent has his body angled sidewise to you, then a low roundhouse is absolutely an appropriate tool. This is standard practice in a number of arts. On the other hand, if he's squared up to you, then a front kick is the one you would use.
Second:
training methods. You are unlikely to find training partners who will allow you to deliver full power blows to their unprotected groins no matter what kind of technique you are using - roundhouse kick, front kick, ridge hand, whatever. Therefore your training will have to modify some aspect of your theoretical real world application.
You can train hard contact to a different target and trust that you will be able to modify the target on the fly in a real situation. This is what you are advocating - sparring with the inside low roundhouse to the leg and having the option to aim a little bit higher in a street fight. Thing is, you can do this just as easily with other techniques - front kicks, uppercuts, whatever. Spar while aiming for a "safe" target and plan to aim for a more vulnerable target if necessary.
You can also train light contact to your actual target and plan on increasing the impact in a real situation. I've done that too - wear a cup and restrict your groin kicks to light taps. You practice developing your kicking power in different training exercises. Once again, this concept can apply no matter which type of kick or other strike you are practicing.
You can also dress your target up in a RedMan suit or some other form of heavy armor that will allow him to safely withstand hard contact shots to the groin. Of course, this will negate most normal, realistic reactions to the strikes, whichever kind you are practicing.
No matter which form of training you choose, you are sacrificing something in the "realism" department. (Personally I advocate working a variety of exercises so that the holes in each training method can cancel each other out.) Regardless, the trade-offs apply no matter which type of kick you are practicing.
Thirdly:
terminology. I'll address this more in your other thread, but I'm a big fan of clarity in language. It's kind of confusing to talk about an "inside leg kick to the groin" or a "vertical roundhouse kick". If I were the one posting this thread I'd probably say something like:
"A low inside roundhouse kick is a good weapon for hitting the groin. You can target the inner thigh in sparring and just raise the kick a little higher to target the groin in a street fight."
