Antenna violations are a distribution. Fabs pick some point on the distribution as the violating point, maybe somewhere between 3-6 sigma. If you violate by a little bit, then you're a little more likely to fail. Violate by a lot and you're a lot more likely to fail. How much violation is okay? Depends on the fab. Some might say what sigma the failure point is, some might not. Antennas are generally not checked by the fab so they don't care.