The million dollar question is if identical twins always have the same type or if it can be different. Some typologies like Cognitive Type
https://www.youtube.com/watch?v=A4w3tDChWTM claim that identical twins indeed have the same type. I don't know if there are any studies on this but I remember years ago watching a TV program where identical twins were reunited after spending their whole life apart and growing up in different families even in different countries. There were superficial differences in adulthood when it came weight, clothes etc. but their non-verbal behavior was strikingly similar despite completely different life environments. So the identical twin argument of type being inborn seems somewhat plausible.
When it comes to very extroverted types with both 1D Ni and 1D Ti such as ESE and SEE, it's not unusual for them to be completely lost when it comes to their own perception of their identity. They really just can't introspect logically.