As I said it is completely irrelevant what the applicant thinks is "normal" or "correct" when he applies to a a key. It is the prerogative of the key-holder to decide what is "normal" or "correct". That is 100% supported by Blizzard.
Could you show me where Blizzard writes "how you are intended to decide whom you invite to you group"?
The only thing I can find is this:
"Note: Groups formed outside of the queue system (Guild Runs, Mythic +, etc.) will not utilize the vote-kick system. Instead those groups will have one party leader that controls who gets invited or removed."
https://eu.battle.net/support/en/article/52363
So Blizzard explicitly gives the right to the party leader whom he will invite or whom he will kick from his group. Blizzard says nothing about which criteria that you are "intended" to use when you pick your party members.