Hey Dr. Who, much respect here, and you're doubtlessly right about all the situations you've described, but:
I love running Blumats in 5-Gallon Smart Pots. Low maintenance, organic soil and tap water. I swap the reservoir out when it feels light, that's it. My whole grow is 600W with 4 plants in a square meter, and I use two blumats per pot, plumbed in a loop with a standpipe. Reservoir sits outside the tent on a milk crate that's zip tied to a foldable synthesizer stand, haha. Totally passive, which is great. I have the option of hand watering occasional supplements, the blumats stop dripping until they start to dry out again, and I've seen some pretty intense roots for a person of my minimal experience. Once I get my organic soil mix completely dialed in and some damn COB lights I think this will be a pretty respectable little rig.
I'll try splitting my rootball on harvest day, I'm curious about the umbrella effect, next run I think I'm going to add some more coco to my soil, with this discussion in mind, but I really can't complain. I've had problems with root binding and rot when using plastic pots in the past, but I was pretty shitty at basic plant husbandry back then.
I'd say they are growing pretty well, here's last week's growth and some other pics of the setup because I have them. Sorry for the bad photos, it makes the artist in me cringe, but you're all used to it by now.
I love the recycled-material grocery bags as alternatives, a buck a piece or less! I have a fairly large collection of Smart Pots already. After I empty them I let them dry, brush them off and run them through the laundry.