444-4D is an expert in the subject, so you can usually rely on what he says.
The key to whether a green coolant is good for your use is the words "low silicate". If the seller claims the antifreeze is low silicate, then it's probably okay to add SCA and run it in diesel engines. Shell includes "low silicate" in their description, So I'd go with it.
http://www.shellusserver.com/products/pdf/Shellzone.pdf
However, 50/50 pre-mixed antifreeze is
ONLY good for topping off your cooling system. If you are going to change the coolant, including flushing the heater core out with distilled water, then you have to use concentrate, not 50/50.
