You both have valid points depending on how you apply the term "flaw" so the argument is kind of silly.
If by flaw you mean it in the dictionary sense of imperfection, then yes, gen Rolexes have flaws. They ALL have flaws, some would be microscopically tiny but as someone said, they are handmade pieces, they will all be flawed from the specification/design. That is a good thing, in my opinion. It makes your watch your watch. I would rather have a watch assembled by someone with care very slightly differently from the next one than have a watch assembled identically by a machine.
But if you mean flaw as in an error, as in the replica scene, then no, a genuine Rolex cannot have flaws. Flaw as it applies to a replica is an error in design compared to the genuine article, so a genuine article cannot, by definition, be flawed. It is a genuine Rolex, you can't compare it to itself. This is why we tend to tell people "Rolexes aren't perfect either" because noobs will go "MY LUME IS VERY SLIGHTLY THE WRONG SHADE OF GREEN" and anyone with a lick of sense knows that the lume is not uniform on gens either, so this isn't a replica flaw, but it is an imperfection, and should not be seen as a problem.