I can't believe I'm posting but thought I'd get opinions anyway...
I'm currently interviewing with a company which I'm excited about joining. I've had a phone interview which covered work history and was subsequently invited to an on site technical interview. This went well and have been invited back again for a full day on site where I will work with the team, do some more technical tests and do a technical presentation of my choice.
Their office attire is casual, jeans/slacks with shirt or t-shirt. For the previous on site, I wore a full suit which is what I have done for every interview ever, even back when I interviewed for part time retail jobs 15 years ago

My concern is that this is a day on site to check for culture fit as well as the other technical stuff.
Worrying about nothing?