Yes, it is easy to bypass, but any one who does so makes a mockery of fair gameplay and thus themselves. I always want to play games the way the devs intend us to, so grey area topics like this can be conflicting. In the early days of legacy when VAC was first implemented, I remember Garry contributing to threads about cheating on the FP Forums.
The forums aren't available anymore, so I can't post exactly what he wrote. I think he presented it more as his personal opinion as opposed to 'do_not_do_this.' I recall that he considered crosshair overlays cheating, but didn't see any way to enforce it as a bannable offense because players could just physically mark their displays which he didn't want to compel them to do.
This puts players in a very challenging position because it is undeniably beneficial and therefore a disadvantage not to use it. I tested this myself by using a crosshair overlay for a single session, and it made the game much easier.
