if its the older bottle/stuff, it is in fact P21S and yes it is cheaper and it is great!
Now, if it is the new stuff (clear plastic bottle) in my experience it is total crap. No suds, unless you mix like 1/4 of the bottle, no lubricity, glides like you have regular wet sponge without any car wash.
The whole "natural care" BS is geared toward those phags that think buying something "green" will save the planet, what a joke