Abanddon : LOL. How old is your son? I think a lot of women react negatively to a complimentary look as they are so sick of guys leering at them all 'looks' get lumped together. Some do have entirely too high an opinion of themselves. And some women I think put up the enuii look to deter unwanted contact.
Me and my gf did find it hysterical on holiday though; I assure you, French girls are the world leaders in this look. We'd drive past a group of teenage girls who all looked well-off, well-fed and healthy, and they'd have expressions of such BOREDOM & MISERY on their faces they'd make the average skate-punk or goth (renowned for their surly expressions) look like they were grinning idiots in comparison.
My son is 21 years old ... And he agree with you (but he don't know if it's only a French woman way of being) I don't know myself but i guess You both are right : if you say IT.
To be clear myself I only care about the way the guys are looking at me ... no matter who or how or old he his ... (in a ferrary or in street the treet with 200 pounds tool in their hand or a brush).