No. I see what you are saying, and it would simplify things greatly, but let me say what I see as one of the raison d'etres of most of the people here:
We are here to break standards, not make them.
By limiting ourselves, we would never see creativity, just the same old, again and again. What if someone incredibly storage use heavy (3.5 drives) and loves to use insane amounts of gpu horsepower? The Ncase M1, or even something micro ATX would be perfect for something like this, but with any standards whatsoever we are constricting the talent of many designers.
Take LukeD's project Orthrus? Would the fact that it is micro ATX remove it from the world of small form factor computing? That would be a waste of talent.
The concept of "small form factor" should be one of space efficiency and clever ideas, rather than raw size and pure specifications.
Hell, if you can make an ATX build with 4 gpus and a ton of 3.5 inch drives all while barely wasting any space, it should be classed as "small form factor". Because, you see, "small form factor" is a concept that is relative to everything else. If it's small for what it contains, it's sff. It isn't a set of guidelines telling you how something should be done, but rather a motivation to fit exactly what you need and nothing that you don't into your next build.
