Hi Diesler,
Placing the pots in just shallow holes would work and that is exactally what Bass has done with a few of his this year. Just remember to only drill drains holes on the sides near the bottom of the pots so when late fall arrives it a lot easier to cut the roots growing into the soil with a flat spade before removing the pot from the hole.
My pots are kept on my back top driveway to help heating up the trees. In zone 5 every measure counts. The other reason the soil in my yard is composed of mostly blue shale which makes for hard digging.
I do think you ought to go with a few next season and see if you can tell if there are any benefits derived by doing it that way.
If Bass sees this he may have a comment or two about his results.
Lou