Platinum requirement is 2000 points. It took around 4 hours of attempts.
It looks like I totally clutched it at the end, but really, it was blind luck. I have no idea how to control the trajectory. I figured it was just timing like in Wii Sports 1, and that is a factor, but there's more to it and I couldn't get a feel for it. A lot of the time the ball would go wherever it wants. Total luck.
Wii Sports Club 100% Playlist:
• Wii Sports Club (100%)