Yes OP, this advice has been around for a long time among top coaches. Rick Macci mentioned it in a video 20 years ago. Girls do not throw as much in general terms.
Sharapova has tossed the football for a long time. Williams sisters have too. I have had my girl toss rocks into lakes, little balls, etc. since she could walk. Years ago I found these little yellow football shaped
things called 'tennis footballs'. Forget where we got them.
Throwing helps the service motion....well more like, is the motion.