Some people live in apartments, simply do not have outdoor areas available. I started indoors gardening with orchids. It is easier to keep them indoors year round than deal with insect pests outdoors.
Eventually the indoors only idea expanded to include bonsai
The floor to my room is carpet so they need to be in the tent because it has a waterproof floor liner. Plus the walls are reflective mylar type material.
Grow tents are great but they are not meant for ease of viewing. With the right lighting they are very efficient because they have reflective sides which is much better than having all your light from above. They are spillproof with waterproof bottoms. The have vents which allow exchange of gasses and complete control of humidity. They allow for a fan or two and you can set up self watering with a wick system.
I also have fans, on 24/7, and I exhaust hot air from the ceiling outdoors. So we are on the same page there. You know how to grow under lights. The only trick will be getting used to how frequently shallow bonsai pots will need to get watered in the light tent. A rapidly growing tree can move a lot of water quickly.
Growing in a pot with coco coir is really not like growing in the ground. The problem is over time in a pot the roots compact the soil. This doesn't happen in the ground. Coco coir is good for starting seeds because the plants are not in starter pots for long. This is why potting soil includes things like perlite. These help keep the soil aerated and slow compaction.
If you have a good root base, just cut off the very thick roots. Do this about every 2yrs.
The smaller roots are the feeder roots that carry the nutrients to the plant. By cutting off the large roots that are meant to support it in the ground, you'll be sending more nutrients to the tree. It will be healthy and as long as you keep it maintained by snipping off what you don't want, you will have a stunted tree for years to come.