Of the ones u mentioned , dfc 210 seems to one of those products that contains flip all , its selling point seems to be what it doesn't contain , ' safe for chemically sensitive people ' it says .
and then lists just about everything it does not contain but tells u little about what it does contain .
It does contain washing soda ... and like the ' microsplitters' and similar products there is probably little else to it .
So u are adding citrus prespray ... which contains what the dfc 210 is missing to become a proper complex cleaning mix , ie a solvent , and a wetting agent .
So bacially u were ripped off in the first place and u corrected it by adding the second product .
The second example ... formula 90 is a complex mix unlike the dfc , but its a powder and the surfactant percentage is low , probably simple due to the manufacturing process , from what iv read to get some of these surfactants infused into the powder , the powder is dropped through a jet mist of the surfactant . So it may not be practical to get a high percentage in there . By adding the bio clean you are adding a good percentage surfactant and thus improving the cleaning power of your detergent mix .