Hi, I understand your confusion however it’s not about synthetic source of Vit B9. Rather, its about the form of Vit B9. Folic acid to useable form requires 5 enzymatic steps to convert it to usable form for methylation. Using 5MTHF skips those enzymatic steps and is the useable form for methyl swap between B9 and B12. Having said that, leafy green are a good source of Vit B9 that can be assimilated and wind its way through the 5 enzymatic steps.
PreNatals with folic acid can actually block the receptors that take up Vit B9 from leafy greens, and the 5 enzymatic processes, where their output does other good things in body. Cynthia