Yes but he doesn't have peak human speed. 40 mph is not superhuman as it can theoretically be achieved by normal people. Superhuman would be above what could be achieved by humans.

Technically it is peak human speed. The article is very misleading. It talks about the max force your legs can withstand which we can do a lot more. What it barely mentions is the max speed our muscles can contract and what not. Humans are hitting peak muscle contraction therefore, hitting the limit

That's why it's theoretical. Spartans are superhuman, processing extraordinary genetic traits, they could run at 35mph at 14 while they were not yet adjusted to their augmentations. So it's likely they can run at speeds above 40mph. But anyways my point about being able to withstand far more then what was placed on Chiefs tendon still stands.