Will it confuse your newborn by introducing bottle feed breastmilk at their 14-day-old?

Not at all. At this point some bottle brand will have teats thats similar to mother's nipple. So giving milk via direct latch, express BM or FM would not make baby confused. The only reason sometimes baby love direct latch because of body smell and comforting. While some baby love bottle feed because they do not know how to suck on nipple or we have inverted nipple. So, my advice would be do all three of this method so baby will get used to the different teats/nipple.

I direct latch and feed my newborn bottle fed breast milk!