I have a 11.5 month old. should we not take into account (whether premature birth, on time or late) when switching from formula to cow milk at 12month?

Transitioning milk: Unless your baby was extremely premature, it is generally advised to transition to whole cow milk at around 1 year of age. Gradual dilution of formula with cow milk has been employed by some parents. Transient constipation is sometimes encountered during this change. Monitor closely for symptoms of malabsorption or allergy, as indicated by gassiness, diarrhea, abdominal bloating or rash.