I threw discus in high school and two years in college, and then did a mess of all-comer meets in the mid 90's. You throw discus in a (usually concrete) smooth ring, not on the grass. It would be really ugly to use the same technique on the grass as you use in the ring, you'd rip tendons out of your knees in no time!

Discus and shot put (also done in a smooth, hard ring) shoes are actually rubber-soled but treadless. They need to be able to spin/rotate on the smooth surface without putting torque on your knees, but yet support your foot. They're totally useless for any other function..well...except for hammer!

When I say "spin" for putting the stone, it's actually a "hop-spin" because I'm wearing cleats on the grass. If I tried the same maneuver throwing shot in a concrete ring, it'd "work" but I wouldn't get the distance I used to get when spinning properly in a crouch.

Best all-time discus throw (with a Masters 4k disc..1999) 148' 5"
Best all-time shot put (with a Masters shot... 1999) 41' 3"