Not sure what you are really arguing here, the rule is what it is. Pogba falls short of being Home Grown by bit over a month. Nationality does not play a part in a player being home grown, because it would violate the law. We got Pogba when he was 16, so there is no issue with him being Home Grown had he spent enough time here because he would have developed with us.
The rule is intended to get clubs to use players developed within the two FA's. Now they don't have to be developed from the time they were 8 years old.
It is as arbitrary as any rule is, so what, not sure why that is an issue with you except you seem to want to argue everything in this thread today.