If you are seeing somebody doing this there either they will be putting them back in the ground right away - as on a landscape project - or into something like sawdust beds. And the idea will be that they are fully hardy types, that can have roots cut back late and not show top damage as a result. Unless they are making a mistake. USDA 6 falls within the routine fall planting being feasible set, with the too cold for it group starting with Zone 5. So there will be some potential for winter activity where you are in USDA 7, as long as recent transplants aren't left to sit out and freeze up during bitter weather, are mulched well immediately after re-planting. Here in Zone 8 contractors may work on renovation projects involving the moving around of large valuable specimens through most of the winter.

Isn't there a thread for this? Ken? [https://www.houzz.com/discussions/moving-a-large-fully-leafed-out-hosta-lots-o-pix-dsvw-vd~2000608[(https://www.houzz.com/discussions/moving-a-large-fully-leafed-out-hosta-lots-o-pix-dsvw-vd~2000608)

Yes, too late. What you describe is a warm season grass and they should not be planted after early fall, let alone divided or a hunk dug up and relocated elsewhere. Warm season grasses have a root system that only responds to warm soil temperatures so as the soil cools down in fall, the roots stop growing. Planting or transplanting now just results in inactive roots unable to re-establish in cold, wet or possibly even frozen soil and the plant will very likely die. Or at least the disturbed portion. Wait until spring and the soil warms and you start to see some new growth appearing before you divide or transplant. And if you have never undertaken to divide or transplant an established clump of ornamental grass, be prepared - they have a very dense, congested and heavy root system and it's a heck of a lot of work and hard labor!!

It is not too late to transplant this. Success will depend on the methods and care used and whether this is a root-bound container plant. If already in-ground, get as large a root ball as possible, even if it means sliding it onto a tarp and dragging it around.