I voted yes for these reasons. 1 if a guy is bending over or crouched down you can see the contrast. Whether it be a str8 across line or indication of a thong or similar. With the 2nd type would have me wondering how much was exposed
2 both also erotic'ish and funny when a guy has Speedo lines. From the back my bro @
cdunstan1 and I call them cotton tails. From the front gives you a good indication how high cut up or barely there the pouch was.
I still haven't found anything more erotic and mind thinking than jockstrap tan lines. Like where was he wearing them tanning and why
I have my own pool and no tan lines for obvious reason. But living in a popular beach city in FL I see tan lines all the time.