Part of it is that people think the more complicated the procedure, the better it is. Another part is that people think that a "green" degreaser is better than that nasty old petroleum based one.

Thinking that "more complicated" is better is just plain wrong. The fewer steps you need to do to achieve the same result is usually better. The Simple Green is a "soap" so flushing with soapy water after is superfluous. But, yes, if you use soap (or Simple Green), it would be better to remove it with water because the degreaser is going to continue to "degrease" until it is saturated with the oil. Adding fresh chain lubricant to the degreaser is just asking for it to be removed, especially if you ride in rain.

The problem is that once you've used water you need to remove it. You can bake it off but that accelerates the oxidation of the metal which is something to avoid. You can let it evaporate but if you live where there is high humidity, that can take a very long time and again rust is an issue. You can chase it off with a water soluble solvent like acetone or ethanol but there goes the "green" factor.

Petroleum based solvents are less environmentally friendly but if you use less of them, they are less of a problem. The chain lube is petroleum based so when it is in contact with the "green" solvent that solvent is considered "polluted" and should really be treated the same way as any other polluted material. The problem is that a cup of petroleum solvent is easier to deal with than a gallon or so of polluted water.

Methylated spirits is our denatured alcohol. It is ethanol...the same alcohol as in sippin' whiskey...that has be adulterated to make it undrinkable. True "methylated spirits" would have methanol added to it to make it poisonous. There are many way to make ethanol undrinkable. One of the less toxic and more common ways to do it now is to add a compound that is extremely bitter.

Mineral turpentine is the same as mineral spirits. Other names may be white spirit, Varsol, solvent naphtha, Stoddard solvent, as well as others. Kerosene is related to mineral spirits but it is a higher boiling cut from petroleum. Mineral spirits evaporates a bit faster and cleaner without being highly flammable. It's flammable but the flash point is relatively high...between 20° to >55°C, depending on the mixture. Odorless mineral spirits has the higher flash point.

Never heard of Squirt Lube. I've tired some other "dry" lubes but have yet to find one that works as well for me as White Lightning.