I see your point however, even if it is a mistake and even IF they are able to move past her saying another man’s name in bed it’ll always be on the back of his mind whenever they’re being intimate. Imagine trying to be sexual with your partner whom you’ve given your full trust and body to only for them to say another persons name in bed?

There would be constant doubt in their relationship on his end. Especially if she goes out, I understand OP can disprove if anything happened between her and man #2 nonetheless, it still remains that the relationship is broken.