What does it mean if a guy changes clothes in front of a girl?

Long story short, I have a crush on a co-worker and I think he has a crush on me as well. The only reason why I can't be sure that he's crushing on me is because he's a very sociable guy but I still see him acting slightly different with me. The thing is, today I was cleaning the shower in the guy's changing room and he came in. He said a few jokes and then started taking his clothes off. I said "Wait, I'll go outside" and he said "no you can stay, I won't be completely naked". What does this mean? I'm afraid this might be a sign that he's so comfortable around me that he sees me as friend and nothing else...
What does it mean if a guy changes clothes in front of a girl?
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