I appreciate its difficult but the firm evidence is available at 10am when they first go on sale. If the club are saying they add in at a later date, firstly i dont believe them and secondly why would they do this?
They tend to be added late on just before a game sells out, normally for lower demand games when an allocation that was set aside for another group wasn't taken up. E.g. 30 of the tickets held back for player or sponsors were not wanted and they add them.
It is noticeable that from a 3k allocation for a higher demand game there are around a 1,000 on sale, but a lower demand game around 1,500. No one believes the 60% claim.