When the roots are in the shape of the pot as you described and then put, undisturbed, into a bigger pot, that's potting up.
Negative experiences in regard to potting-up, where an undisturbed root ball is placed into a bigger pot with more soil around it, vs. doing a repotting, as described below, can give rise to old wives' tales about plants not liking to be repotted/disturbed. Potting-up a root-bound plant that has roots surrounding the outside root ball often lead to this negative experience because those roots had adapted to accessing oxygen around the outside of the root ball and surrounding them with more dense, soggy-but-airless potting soil will likely lead to suffocation.
The reason bonsai masters are able to keep potted entities alive for hundreds of years is because they care for the roots by trimming them and changing the soil. A plant grows from the roots-up, so if the roots are not healthy, gorgeous foliage will decline &/or no flowers can form. When you unpot a plant and find a pancake of roots at the bottom, chopping that off will give roots a chance to grow normally again for a while and will make removing the old soil easier.
