I did a similar thing to be honest. Was doing interview rounds last week for very big firms. 2/3 I went in fully suited, got far in the process. The last one I wasn't too keen on, wore just a shirt and jacket no tie, argued with the interviewer, made them backtrack... ended up having 3 business teams bidding for me to join their team at a more senior position.
Sometimes interviews and hiring just works strange.
For me it's:
- Be confident
- Be passionate
- Share your beliefs if you can back them up, aka I disagree with X theory in this circumstance because of xyz
- Don't talk bs
People like people, horrible phrase and said 1000's of times, but it's very true unless you have someone hiring on a power trip.
But I agree with the main premise, you should always wear a suit. But by all means you're allowed to experiment and learn with interviews... if it's not your dream job, mix it up, try a new approach, what is the worst that can happen?