Viral load being undetectable ( and extremely low risk of transmission, never at real zero risk ) at the moment of test does not mean that viral load remains that low continuously.

They are couple forgotten doses away from infecting a retard engaging in high-risk activities, or a rape victim.

Oh and turbo-sluts already managed to brew a recombined strain of HIV that bypasses the ''prep'' anyway. Through selection pressure, strains that bypass these treatments will be the dominant strains eventually, which means highly drug-resistant strains.