Agreed. This is a case of an untrustworthy "authority." It is in G2A's extreme best interest to pretend there's not a problem, I wouldn't trust any numbers that they put out as if they are authoritative.
I should also note that I would trust numbers that indie developers are putting out. If things were working the way G2A claims, indie developers would be getting paid in the initial transaction and they wouldn't have a problem with key resellers to begin with. No incentive for them to lie in this situation.
(not that anyone is implying that they shouldn't trust indie devs: but in case anyone is wondering where a more credible source for information is, I feel like that's a good place to look given the lack of incentive for them to be lying about this)