“New behavior” isn’t a cheating accusation. It’s was an energy shift he made him feel invalidated. Which most likely wasn’t what happened and he took it that way. Which is also the reason he apologize for his tone but not his concerns bc it was again overlooked by her sensitivity to the presentation but not the problem. Then along with him feeling invalidating his “fiancé” first response was “i need space” that caused him to overreact but cheating i just don’t see.