Is it? I may have misread it, but surely if they realise that someone is trying to get in with a ticket under a different name, they should be rejected on the gate, but no sanction applied. As the son said, if they'd realised it would have given their parent a ban then they wouldn't have...
The very worst part of it is that the steward who carried out the ID check let Fan C and Fan A attend the game, and then reported them afterwards. If they had just rejected them on the basis of the ID check, none of this would have happened.
Being cynical, it's almost as if the club wanted to...