If OG simply had to sign a BTC message from HIS keys it is debatable if the airdrop value should be his or not anyway, because they are OG's keys..
The amount of GBYTE airdropped was based entirely on the Bitcoin holdings on the address. So if someone joined by signing a message from an empty private key, he got nothing.
Is an exchange a scam if they claim airdrops on their keys that are full of customer funds and not disperse these claimed values to the customer?
Some exchanges have indeed done that. But what if it's just their local system administrator who claims it for himself instead of the company?