You spend about a third of your life at work, it seems to me that you should try to make it as enjoyable as possible.
Being friendly should suffice, not all of us want to get too personal with the same people we might need to have professional arguments with.
We're all different.
Edit: Not to belittle your son's wisdom, of course. I totally agree.
I think he mostly got it from my wife and I sitting down with our children after having a fight and telling them that we're still mom and dad, we've put it behind us, and it's okay not to get along all the time.
In some ways, I find it's more enjoyable to not be friends with my colleagues; to keep my personal life and work life as widely separated as is feasible.
Of course, intra-office competition at that level is highly destructive but that's what people are acculturated to.
But really this is just more a case of I wouldn't be comfortable talking about my deepest desires with a random person. Sure, once I get to know someone a bit, I'm fine to do that...but a random interviewer? Eugh.
[1] That said, my Russian partner would not consider them friends. Friends in her world are people you can count on for anything and how many of us can say that about our colleagues?
"hey, what'd you do this weekend?"
"well, my friends and I run a historical re-enactment society where we all go to this remote retreat in the mountains, dress up as Nazis, and pretend that they won World War 2."
and you know what, if it was possible to just hold your finger down on the "rewind time" button for 15 seconds to just never ask this kind of friendly question, life would be so much easier. how do you reply to this? just stay out of other peoples business if you have to work with them.
I think the significant concept is that in the long term, there are very strong similarities between the mechanics of being a coworker, and those of being a friend.
So definitely it makes a lot of sense to "investigate" that way.
This holds two things constant: You and the job.
On-the-job training is inevitable. The question is what you'll primarily be trained in: Office politics, or some other skillset which will actually go on your resume.
Similarly, the job will inevitably change if you're around long enough, and that's the nub of the meat of this: It's an old adage that you should never marry someone to try and change them, because people don't change, they just become like they are, only moreso. Both ends of the equation change, but they change around a solid core which was formed decades ago and will not be modified except through some serious event.
So personality matters quite a bit if you're looking for a marriage. If you're looking for a hookup, it only matters on the extreme ends of the bell curve.