It is not rubbish, it is common sense. If you are paying for a heavily discounted, promotional product - that is what Advance tickets are - you should not receive preferential treatment to those who are paying full price, on top of the heavy discount you have already had. That is an obvious concept and would apply anywhere, not just on a train. Why on earth should a season holder have to wait for the next train to enable those paying pittance to travel instead? The one train Advance ticket users have 'tied' themselves to should not be one to which full-price ticket holders are then denied access. Perhaps you should suggest that to a few commuters who pay four-figure sums for their season tickets and see what their response is?!
I thought season ticketed were heavily discounted, promotional products? With them, you can go regularly at a discounted price. Plus they have flexibility included in the price, you can go how and when you want as regularly as you want.
On other hand, advance tickets are cheaper because they are completely limited. Not just to an operator, but to a particular route at a particular time. They make sure all kinds of trains at different times are used to help fill them up. But you lose any flexibility with the price drop. On the other hand, open tickets are more expensive, but you get flexibility. Either wawy, they are balanced.
The key thing is you can reserve seats with either. Want flexibility, reserve seats for free and be happy but pay a bit more for the ticket. Want less flexibility and have a cheaper ticket, pay a bit less and get a reserved seat, again for free. There is nothing stopping those paying more for more expensive open tickets from reserving seats.
Saying that those paying less for a more restricted ticket should get less entitlements seems a bit wrong. What about those that pay for a more restricted ticket (e.g. Operator specific), should they get less entitlements too, as these are cheaper tickets?
If people want the flexibility to leave it to last minute, go on any train they want, any operator they want thethey will pay more. Thats one issue. A completely seperate isssue is if they choose not to reserve a seat (which I believe can be done up to 2 hours before the train departs it's first station?) the they won't get one, but they had that choice and option.
Advance forces people to reserve, yes, but anyone can reserve. I think its pointless to try to link reserving seats to ticket types, as theyre completely separate issues.
If the main complaint is that people who book in advance, know what they want to do, and limit themselves to exactly that, with a ticket that can't be refunded or changed and becomes a useless piece of paper upon missing the train get a cheaper ticket compared to an open ticket, that's a different discussion, yet I think the answer to that is straightforward too - the more you pay, the more flexible it is and the more open it is to you. The less you pay, the more flexibility you give up and the more you fit in with what the rail operator wants, but in turn you get a cheaper ticket.