I think the info is just getting crossed up here.
Your plants are healthy, just could benefit you in your outside grow with a bigger pot for bigger yield. As long as the little amount of soil you have them planted in is Not Miracle Grow, time release soil, or sick plants your are just transplanting to a bigger pot and adding good soil for your cannabis future in a new pot.
Washing the root ball is fine and is do able but if that soil is not some sort of problem there is no need to remove it and add the potential risk of more stress then is needed to your plant.
I would highly recommend roots to be washing if the plant was in MG, time release soil, had root problems and need replanting.
Just want to make sure the information you are getting is clear about why you are transplant and save steps if they don't need to be taken.