Why? If I was at Dundee, Stranraer and both Dundee Utd games but due to another commitment could get to the semi final but someone who has only been to one game (the semi final) should get priority over me and other season ticket holders.
Your also missing the fact that it is an implied term of the season ticket that ST holders get priority on sales of these types of tickets (it was written into the renewal letter).
I doubt I'll be unable to get a ticket anyway but why should attendance at one big game get priority over anyone?