"I disagree that there is a significant correlation between expanding population and an expanding economy."
In any functioning economy there is obviously a correlation.
Bodies have jobs, generate income, and they buy stuff meaning GDP.
Government spends on social services per body, meaning GDP.
Not only are 'warm bodies' a part of economic growth ... 'warm bodies' are the very basis of economic growth in most of the West! If you take out population growth from US economic data, it looks a little more like Europe. If you normalize for lower rates of children ... that explains a huge amount about lagging economic growth in the West.
Populations that require homes, cars, services, food, mortgages - that's what drives the economy.
So to your point - in a dysfunctional scenario, more bodies means problems, but overall no.
How do you think America became the most powerful entity in the Western world and in some ways in the world? And not Sweden?
The story of American economic growth from 1777 onwards includes a lot of things, but if you measure up against Europe, what mostly stands out is body count.
Also - remember that growth is measured in GDP, not 'efficiency' - so as AI does 'more for less' it's technically 'bad' paradoxically, for the economy, as you point out. But as long as we figure out a way (any way!) for the surpluses to be distributed, they will be spent, hence 'growing economy'.
Canada's economic strategy is fully based on body count. The nations banks drive our strategy, and they can't grow any more through competition or innovation - they can only grow through more mortgages, which come from more bodies. So they push for large scale immigration, which is in their self interest.
'AI' is not how the economy will grow.
A sea of new homes, out to the horizon, with a Starbucks on every corner, an IKEA in every neighbourhood, a Toyota in every driveway, and a dozen prescriptions per home ... this is how our current economy 'grows'.