Their lame reason will lose their potential customers. I have seen a Chinese model of Samsung galaxy note 9 with Android Q. I have seen inbuilt app lock feature in that device. So implementing this in India model is not a big deal for them. But it seems they doesn't care for their customer's need
if your device is s series...then you can apply any 3rd party app locker exept s secure which is not compatible to your device....Samsung strategy was to give Knox security and secure folder inside s device....but not s secure
The UI experience and usage of third party app lock is very dull and not satisfying. Also, I cannot find some trusted studio/developer/publisher for such kind of apps. And, these apps doesn't lock your app properly. While using third party app lock, if you open recent app list from navigation bar, you can see content of your locked app.