There is no difference. St holder is responsible for person he buys a guest ticket for and would be same if he passed his ticket onThe guest tickets thing (and the club not knowing who is sitting in the seat) is definitely an anomaly, but still managed by the club.
That's different to allowing, say, 2000+ Albion fans being free to distribute their Man United or Chelsea tickets as they wish.
Honestly, can you imagine that?!
(Don't get me wrong - I wish we still had a book of tickets, to use as we wished. But, also, I can see why the club wants control too.)