Participants took folic acid (lab created), not folate (the form found in nature) which has been shown to be far more absorbable. Folic acid also binds to the folate receptors, preventing folate from food being taken up. In people with MTHFR gene mutations, folic acid is contraindicated. Anyone with such mutations should be avoiding foods with added folic acid. Folate and folacin seem to be ok. MTHFR is already associated with increased cancer and heart disease.
No mention was made whether the participants had MTHFR mutations, perhaps because the cohorts started 20 years ago and cheap sequencing wasn't yet available.
All it tells is that more actual science needs to be done here. Also the article was classic poor science reporting with obvious bias.