My 2 cents:
Based on his practiced high jump 3-step approach and how closely it follows Tex's description, it looks like he almost certainly took 3 steps to dunk it. You do need a lot of momentum to sail across the free throw line. It's hard enough to believe anybody did it in 3 steps but he had one of the most impressive looking strides + acceleration in just 3 steps that I've ever seen out of an athlete. Most high jumpers of his time took at least 5 steps and most took 7. At that age he was still thin - but he had a lot of strength in those long legs.
I also don't think Wilt is an outright liar
like some people do, I think he's more of just an entertaining "story teller
" in the sense that he embellishes things to get a point across - it just sounds ridiculous to people that don't understand this because he's embellishing things that are already impressive or otherworldly enough that they wouldn't need any exaggeration. If he's referring to the foul circle - he's likely embellishing his ability to free throw dunk. But has anyone considered that he might be referring to staying within the half-court circle? His 3 strides might have stretched him out that far, just a thought.
Check out his 3 stride high-jump - his first few approaches show very
impressive speed and explosion by only his 3rd step from a dead stand-still.
Check this out too. His stride rate when he opens up the throttle with those long legs