Breeders want to sell seeds. When they say 8 weeks, that is 8 weeks from the first buds starting to form {if they are pretty honest} You have to take into account the time it takes the plant to trigger from veg to flower mode. Later on when you have a few grows under your belt, you will learn the times for each strain. Most of the pros do a room of clones from the same plant so the flower times and stretch is the same across the room. I've never grown indoors, but from what I hear, managing your canopy height is a PITA when you have several strains.
On down the road if you could get a veg and a flower space, you can keep a mother in veg and take clones off her. That way you can more effectively use your time and electricity. You time it so your clones are ready to go into flower when the plants in there are ready to be chopped. Since it is always at least 8 weeks for flower, you can veg your clones a little longer to get more size to them.
Also light is the main factor in yield. 4, 6 or 8 plants could make just as much weight as your 22 with the same light. 8 would be the max most folks would try to flower in a 4 X 8 space. That gives you a 2 X 2 space for each plant, or 4 sq ft.