I have a friend who fits ISTp descriptions pretty well, and I'd have little doubt in typing him as such, except for this - - one of his main hobbies is writing love poems, he even wrote a couple of books.

However, this is something he reveals to very few people -- he usually keeps it a secret. He's an engineer and would not like people at work knowing about it.

Could it be a manifestation of the hidden agenda - - or it means nothing related to type?