It's not uncommon for interviewers to ask a few warm up/intro questions and then proceed to more advanced questions--so if you didn't get a few questions right,

It's not uncommon for interviewers to ask a few warm up/intro questions and then proceed to more advanced questions--so if you didn't get a few questions right, you may simply have missed some easy ones, so they didn't ask you the hard ones. This would leave you the impression that you "almost" made it, when in fact you may not have come close.