ball deflected off F1

[shipwreck]

NFHS rules. Can someone explain the reasoning (if I understand it correctly) the reason that a hit ball that contacts the pitcher and then goes to a place where another fielder could make a play, but the fielder is interfered with, interference is called since this is considered making an initial play, but if the ball hits off the pitcher and then strikes a runner it is nothing unless it is intentional? What do other rule sets say as far as this goes? Dave