If they are shipping items that require a prescription without verifying a prescription, then they are illegal, regardless of what the items are

Online contact lens sellers (at least ones I've used) do verify your prescription. Is it up to FedEx to investigate whether their customers are required to and actually do verify prescriptions?

how do you know the prescriptions don't exist/weren't verified?

My point was merely that this (allegedly) was not just some automated anti-fraud measure as some people speculated here.