Sounds like a non CO2 approach to me.
Or maybe Excel and low light and or CO2.

We grew a 420lbs Hungarian mammoth Pumpkin when I was a kid.
Took 4 men to lift it. We had the largest pumpkin on the block that year!!
But then we grew 90% of the food we ate other than meat and milk.
No, I was raised in suburbia, but we had 20 acre farm land in KY and when I moved to IN, we had a 70 acre hardwood forest. Seems I was a lucky little dirt bag

Regards,
Tom Barr