Wait, did I somehow get married to all you people, feels like it with all the completely manufactured straw man objections?
Criticise that concept of putting more soil where the plant needs it and less where it doesn't. The concept is sound so if you can't criticise the concept then it's a matter of working through the objections.
Doesn't need the zip, I'm just thinking of different ways it could be done. But the whole point is simply to look at what is needed.
You often see a little seedling in it's final pot, sitting in the middle of a vast ocean of soil with a little pool of damp soil around it, why? Because you don't want to transplant. So the seedling now sits in the "neck" of the grow bag as if it were in a six inch pot. It's the natural way a plant grows, the deeper it gets the more it spreads out.
A short zipper near the neck could be added for those who need that, but a 6" hole should be plenty, and when the bag was picked up by handles on the top there would be less likelihood of shifting soil that could damage fine roots.