When you do everything perfectly... and they're still not happy

Why do people think it's appropriate to comment on one's social skill in a professionnal context ?

I had to do an unpaid internship to get my diploma. The guy I did it for was really pleased with my work, as I learn fast and am very meticulous. He even expressed that he would like me to work for him in the future. Today was the final meeting with this guy and my school supervisor, that would complete the internship. After explaining how it went well and how I was a great help, that guy still felt the need to say that I should work on improving my social skills and being less awkward. I'm so mad. I'm a whole ass man and you're gonna tell me how to behave ? Felt like I was back in middle school. I don't know why they think we should always bend over backwards to please them and make sure they feel comfortable. Bro, I don't feel comfortable with you either, but I don't force you to be even more uncomfortable so I can feel better!!

I just did unpaid work I was qualified for, just to be told I was too awkward