Well that article says this rule is for displaying the tree. It was new to me as I shose pot based on trunk width not tree hight. But I guess one gives the other for a mature tree in proportion.

But for this young tree in development with decades until first show I would suggest biggest possible pot or even planted in the ground a few years.

Small pots is never better for tree health, growth speed or development, bigger pots are.

Enlarge your pot = rejuvenate the tree and gain trunk and branch thickness
Reduce the size of your pot = aging of the tree