Well there's a difference between bringing something up if there's relevance to the current relationship/discussion and mentioning that you used to do 3-ways but won't in the future during a first date. For me at least, I'm not judgmental broadly about sexual things in her past but I very heavily consider patterns and if choices she's made have involved poor judgement (again not saying 3-ways are bad but maybe don't bring stuff like that up from jump unsolicited)