From the same Wiki page:
The patented formula was: 4.0% isopropyl alcohol (a highly volatile solvent) 1% ethylene glycol monobutyl ether (a less volatile solvent), 0.1% sodium laurel sulfate (a surfactant), 0.01% tetrasodium pyrophosphate (a water softener), 0.05% of 28% ammonia, 1% of a dye solution, and 0.01% perfume, the balance is water.
But as noted, the formula changed to new solvents. The problem with either formula is the level of glycol ether, and type now with the new formula. Ethylene glycol monobutyl ether is the prefered solvent and universally compatible with most acrylics. n-hexyl ether is not compatible with all acrylics. Beyond the type, the percentage needs to be higher. All that alcohol is a problem also. The gycol ethers act as what's called coalescing solvents and are what allows waterborne emulsions to be miscible in water, and necessary to add alcohols. Without the proper level of cosolvent(generally 4-7% minimum), the whole paint mix could become unstable and no longer be water soluable. Thus, the paint components separate and you get a clumpy mess in a bottle or gun.
I'm just as guilty of trying to shortcut it. I have a bottle of Autoair flo yellow that I blew out a few weeks ago. Thought I'd thin it just slightly with water alone, but the next day I had a bottle with a layer of water, resin, and pigment. Scrap! I've done it many times before with no problem, but every batch of paint is different. If the factory was adjusting the viscosity with just water, they could have stretched it to the limit, and I just pushed it over the edge with what I added.
I would say that if you are using Windex and there's no problems, then keep at it. Just keep what I posted in mind if you ever use it with a different paint, or even color, and have a problem that you can't explain.
Just food for though for everyone.