I agree with the overall point that it doesn't matter.
I'll just add/disagree: "body count" is just a phrase to indicate how many people you have slept with, and OP just asked a question, didn't indicate a position on the matter. I don't think it indicates immaturity to use a short, easy-to-understand phrase to communicate an idea.
Even if hypothetically immature, I think people may have an emotional reaction even if they agree with all of the above. So I think it's an interesting question.