With all do respect, I gotta disagree. Everything I grow, every kind of plant, in every size container from less than a gallon tp 30 gallons.
The plant below was grown in a 3 gal pot with living soil. Next to it is a 30 gal pot. It was an afterthought. Found a magic bean in some weed so decided to germinate it. It didn't go outside until mid-late June. Zero effort put into it other than feeding and watering. And the feeding was really just what might be left over from feeding the other plants. The pic on the right is from Sept 16. Still managed to pull about 100 g from it and it is some of the best smoke from that season.
View attachment 2268912View attachment 2268913
This wild flower is in 2 gal living soil. It was about 8" at transplant. She seems to be thriving, no?
View attachment 2268914
The notion that you can't have a thriving rhizibiome in a smaller pot is just plain hokum IME.