with no training....like if the coach randomly rolled out a portable 10-foot hoop on the first day of fall practice and said "Ok Boys, let's see what you got? Can't dunk? Can't run for this team!"
I'd say about 80% of them could probably at least throw down a regular dunk if they were motivated. Definitely could with a few weeks practice, like if they heard a rumor about the dunk test from the year before and did some dunk reps at the local park a few times during the summer.
I mean they are running 80 miles a week, always on their legs. Those legs have got to be STRONG with all that running.
But a windmill? I'd be surprised if more than 2-3 people on each team could windmill. That takes some real hops.