> Apparently this form of B9 absorbs better if it’s combined with the methylated form of B12 (methylcobalamin)

B9 and B12 are interdependent. When the body uptakes cobalamins, the ligands are pulled off and replaced with ligands sourced from other processes. IIRC in the case of methylcobalamin, the methyl group is pulled off and replaced with a methyl group that’s moved over from methylfolate via a riboflavin-dependent reaction. Been a hot minute since I looked into this so I may have some details incorrect.