Foster generated a ton of force. This is a fact, regardless if he had faced 30000 different styles or not. The claim that these types of roundhouse kicks are fundamentally "weak" is disproven. I am not advocating he kicks the hardest, only that they are indeed just as potentially powerful, and not the way old school advocates likes to portray them.
Foster had the good sense to turn his hip over. That IS the more powerful version.
Sent from an old fashioned 300 baud acoustic modem by whistling into the handset. Really.