cutting roots for in-ground transplant is extremely beneficial. however, there is right way and a wrong way, and anything other than the right way is wrong and detrimental.
a bound plant will explode with scoring and transplant. keep in mind, this is ideal, well fed, fully established plant to start.
at the point of binding, roots are looking for new space. this is great, as you're about to give them some. the un-potting is referenced above. now, if you have nearly solid white wrapping your soil, here's how to score for a boost of root growth and reestablishment.
at your pre-prepared site, un-pot your plant. you will have a mostly white, wrapped root ball in hand.
score in four quadrants, with a sharp sterile knife (doesn't have to be sterile, but results are tremendous). in other words, rake the root ball in four spots, x and y axis.
immediately transplant and pack soil gently but firmly.
now comes the important part of this process...
saturate soil with nutrients and vitamins/hormones (superthrive, don't mess with anything else). use super thrive at one teaspoon per gallon, nutes at half strength.
shock will last for 16-36 hours, and after the plants will explode. slowly first, then crazy growth. each broken root will grow hundreds more as 'feeders', which will become the new root base. the tips that die from scoring quickly rot and are used for new growth.
i did a lot of playing with roots in dirt and hydro. scoring done proper is like topping done proper. superthrive i swear by, best root accelerator i've ever come across.