Because the player in question hasn't come forward. I presume there is no other way for the AFL to know.
Essendon however came forward so there is a perfectly logical reason.
BTW can you please provide the quote from Gil. Ta love.
You presume incorrectly. From ACC report (which, again, I suggest you read):
"Legal provisions prevent the ACC from publicly disclosing detailed information about the
nature of the matters contained in this report. This includes the disclosure of information
specifically referencing players, clubs and any information that could identify other
individuals involved.
Particular sporting bodies have received classified briefings on
matters relevant to them."
The AFL know who the clubs/players are in the report! This is a cold hard fact as seen written in black writing above. They know who the single player is, the know who the club is. Today, they TOLD US the club is Essendon when the question was asked.