I think the source of the confusion might have been the use of the word "any". If you had said "like a muscle", that would have been unambiguous, implying that it isn't one but is only being compared to one. Whereas, "like any muscle" is something you might say of some particular muscle in order to point out that it is like its fellow muscles. I do not mean to suggest that "like any muscle" is in any way incorrect. The interpretation of what you said as saying "while not a muscle, it has this in common with all muscles:[...]", as a stronger statement than "while not a muscle, it has this in common with a typical muscle:[...]", makes sense of course, and I think it or something very similar would be the most common interpretation.