That doesn't surprise me, other than the fact that it's Australia, where I think we assume that children grow up sporty by default, especially given the relatively benign climate. We have exactly the same concerns as most parents regarding screen time. But it's tricky; I don't know what a family like ours would have done 30-50 years ago. I honestly believe that children spent more time bored out of their minds in 'the old days'.
Maybe my wife wouldn't have worked - and more than likely, I would have worked away from home, rather than mostly in it, as I do now. That might have allowed more opportunities for children to congregate at our home after school. A non-working spouse may have spent more social time with others in a similar situation, thereby forcing their children to spend time together; company makes outdoor games much more palatable. As it is, given the age gap between our children, there is often no one for our younger child to play with after school, unless play dates have been arranged. We are busy, her sibling is doing other things. Other than sports during school or extra-curricular stuff, she can't really play ball on her own for long - and I can't imagine her jumping up and down by herself for longer than a few minutes! So yes, we allow screen time but also encourage reading and art time. Wherever possible, we encourage outdoor time and whatever physical activity we can share together.
Our eldest child, in spite of exposure to screens, is sporty and competitive. She is in many of the school sports teams and also participates at competitive level in extra-curricular sports. Our younger child is not so sporty, but enjoys some sports and many outdoor activities. But she is very capable indeed academically and very talented artistically. Who knows, maybe she will find her sport and become hooked in due course.
My only wish is that there was more in the way of compulsory sport/outdoor activities at school. The way school hours work has not really adapted for the modern age and I wonder if one could kill two birds with one stone by extending the school day to accommodate an hour of physical activity every day.