Well, the statement you make is highly debatable, and one reason for this is being the label of “well-dressed” debatable itself. I don’t know what your idea of “well-dressed” is.
Like for me well-dressed means looking smart enough to make heads turn when I pass by (I think most of the women thinks so), but for my mom, “well-dressed” means being dressed modestly, and simply dressed.
We however, are talking about men here. According to me, the general idea of a woman being “well-dressed” is that she’s looking attractive enough to rest their eyes on for a while (please don’t take me wrong here, that of perverts and creeps is a whole different story and understanding).
So taking this as the most-accepted definition of “well-dressed” for men, I’d say that it’s not only being well-dressed that makes men look twice at a woman. A man may look at you more than once for the kind of hair you have, even if you didn’t get time for a good hair-do this morning and are traveling with just a messy bun.
Although, a man may also be caught admiring anything about you and not just how you are dressed, it can’t be denied that dressing style is one of the foremost things that men notice in a woman.