This is not quite right. I don't think any other pharmacy tests what they dispense. It's expensive, difficult, and the FDA doesn't seem to appreciate that their risk management strategy is being second-guessed. They recently issued a long warning letter to Valisure for doing it [0].
Note that ValisureRx (consumer pharmacy that dispensed lot-tested drugs) was sold to Medley Pharmacy, which just folded. Valisure is now just a testing lab.
Finally, it's not just a chain of custody thing. Even big generic brands and name-brands source a huge amount of active pharmaceutical ingredients (APIs) from China and India.
Note that ValisureRx (consumer pharmacy that dispensed lot-tested drugs) was sold to Medley Pharmacy, which just folded. Valisure is now just a testing lab.
Finally, it's not just a chain of custody thing. Even big generic brands and name-brands source a huge amount of active pharmaceutical ingredients (APIs) from China and India.
[0] https://www.fda.gov/media/163682/download