I gave a single example of why an app might fail at facial recognition in some cases. Obviously I wasn't suggesting that would be the case for every app that doesn't work. Suggesting I was is a strawman of ridiculous proportions.
I also didn't say anything about ML training data in the post you replied to. My point was about facial recognition app developers not testing with a diverse range of inputs, which is why we see apps failing in public when people try to use them with inputs the app hasn't been tested against. If the apps were well tested those cases would have been caught before the public ever saw them.
My original point stands - if your testing sucks then it's very likely that your app will suck too. There will be problems with it that you don't know about, and the users will find them very quickly.
Do you have any data showing facial recognition doesn't work well on black people? My understanding is that this is an urban legend - it's not true, the algorithms work fine assuming a decent quality camera and video (same for everyone).
I also didn't say anything about ML training data in the post you replied to. My point was about facial recognition app developers not testing with a diverse range of inputs, which is why we see apps failing in public when people try to use them with inputs the app hasn't been tested against. If the apps were well tested those cases would have been caught before the public ever saw them.
My original point stands - if your testing sucks then it's very likely that your app will suck too. There will be problems with it that you don't know about, and the users will find them very quickly.