I saw it as more the question that if you don't want to marry me, Id like to change my name so we all (kids and us) have the same last name? And for him to say "not sure" seems to say without saying I'm not that into you?! If I read that right...?
I changed my name when i married (was quite young) and saw it as more loyalty towards my husband given my father was a a@@hole. Couldnt wait to have no association with him. Helps that I was 1/3 girls - we all changed our names. No dependence here ☺
Edit: If I were to get divorced, I would keep my married name - my professional career was built with it (all testamurs have it on them) and its the same as my childrens - and its actually much nicer than my maiden name 😅
Marriage is important to me and was a necessity for me to agree to kids (albiet 4 years later), but I am a Ms and don't wear a ring either - DH never takes his off. We are committed.