My brother (oap ) missed a game. Box office gave me a ticket for his granddaughter (12) to use his seat. (No charge) Cancelling out his season pass for that match. Safer than sorry.
They arent transferrable its in the T's&C's as you correctly point out, however many people will happily let a friend use a ticket if they cant make a match - personally I dont see much wrong with it if its for the same category. I think its a standard term for all clubs though and most turn a blind eye unless used to allow someone who isn't wanted in, such as someone banned for example, it also gives them leverage to take action against the ticket holder if the person using the ticket misbehaves. I think a few years ago a club (Fowls?) tried to really enforce it with photo id and it wasnt very popular and soon dropped