I find that more than 90% of new roots grow direct from the exposed cambium of the cut ends of roots so if I want roots to divide and ramify I know to chop the roots at that spot rather than cut long and hope for roots to grow back along the length of the root.
There could be some differences between species. I have more experience with deciduous but from what I can see JBP roots respond very similar.
Chopping thick roots to short stubs is not a good idea on all species. Trident maples, most apples, privet, banksia, most ficus and some others can have roots chopped hard. I often make initial root chops on tridents so that the roots are similar length to the trunk diameter.
Junipers and pine roots can't be chopped that hard. They will often die if all the roots are chopped back to stubs.
There's a whole range of species that have in between tolerance for root trimming.
Knowing which can be chopped hard and which don't do well is from experience or research. If in doubt, err on the side of caution and leave extra root just in case.