After 26 years of gardening, I have never loosened the soil from the shape of the pot. I just plunk it quickly into the hole from the pot. Making sure the hole has good growth room around the new baby. In fact, it bothers me if the new plant drops it soil around the roots as I am moving it to its new home. And I do not go crazy with fertilizing or leaf mulch. But in a very new garden area, I may have inspected the soil long before new babies arrive and if the soil is too hard etc. I will work that area first with peat and top soil.
as I am thinking about it, I think its also common sense. if you run across a pot of something, and it has become pot bound and really hard, then I would help it some prior to settling it into a new home.