I'm not sure about a heavy ball mattering, but the heavy racquet is probably a good thing to force core usage. In my youth, I used to make extra money doing condemned house demolition in side jobs. Swinging a sledgehammer is a perfect example of having to use the core.
The same can be said for choosing the correct bowling ball. Too light, and you end up throwing your arm out and/or lose complete ability to control the ball. Too heavy, and you end up not being able to put enough spin and speed on the ball.
When I changed to a heavier racquet (went from 8.9 to 11.7 ounces unstrung), my game instantly got better and my strokes got more consistent because I was using my whole body more as opposed to just arming it.