What's so important about the type of someone else?
But just to answer the question... I've seen more ENTPs thinking they are INTPs. Myself included.
Why?
Because we're bad at socializing. We can't remember the details (eg. names...) needed for making contact to people. If extravert was synonymous with "people-minded", I don't think there would be any ENTPs.
But extravert is more than that.
"Needing input to be productive" and "craving attention" are other tell-tale signs of extraversion... and ENTPs (at least this one) score high on those.
The functions are another way to discern between E- and INTPs.
IF we can use Ne in communication with other people (discussing theories, improvising nonsense stories,...), we won't feel drained and won't feel the need for an I-style replenishing. But these occasions are less frequent than the usual smalltalk and socializing. So yes, an ENTP will answer yes on the question "after prolonged contact, do you feel the need to be alone for a while?"
If the question is "Even if you're having a good time with other people, do you still feel the need to be alone once in a while?" my answer would be a solid no.
Thats like the ENTP I know, he is convinced he is an INTP, and some days he says he is INFP
INFP! I've been convinced of that, too. Not in these terms, because at that time, I didn't know about MBTI. But I was convinced that being reigned by emotions and personal values was the right thing to do to be a real human being.
It didn't really work for me. Wonder why...