You dont understand it because you are not a submissive with extreme masocistic streak with a need to be humiliated and demoralised with a large dose of pain on top !
I have experience with these types of guy and even among the "Sub" mindset , receiving kicks to the balls is pretty "out there" . Also , many guys on AW who claim to want to be kicked in the balls are pure fantasists who are more into talking about it on phone/cam than doing it for real. I accept there are SOME who will pay for this service but they are very few and far between.
I think a lot of AW advertisers will talk about this on their ads as they see it as a very easy way to earn ££ , but the most many of them will ever get is guys ringing up to ask about it who never show.
I havent read the FR but id take it with a pinch of salt.
Ive got quite a few hardcore "slaves" and even those guys wouldnt want a ball kicking !!
On the other hand of the coin , many "responsible" mistresses wont do this activity as it comes under the "things that could cause permenent harm" . A good mistress can cause pain/humiliation with no lasting effects
As im sure all you owners of balls will appriciate , its actually quite dangerous and can cause all sorts of ruptures