Most any 922r discussion I've ever seen usually comes to the conclusion that no, the ATF isn't usually going to examine all your guns for compliance. However, if they decide they want your hide over the barn door for some reason, they'll use whatever they can to do it.
Although it is unlikely you'll ever be in a position where the government even discovers noncompliance, let alone charges you with it, I recommend that you follow the law to the best of your knowledge and ability. On the AK, 922r compliance is incredibly easy to attain. The trigger group itself is inexpensive and the effort required to install it is minimal.