hmm, i took it to mean only leave 1/2-1", as the problem im having is the plants i bought have 3-4" roots and it is difficult to plant as the roots keep poking back up through the subsrate
If I had an Amazon Sword in an old setup that I was transferring to a new position it would hav 1ft plus roots.
I would then cut them so they were about 1 inch long and plant in the new position setup. It will then be stagnant for a while and then all of a sudden burst into regrowth.