It still doesn't change the fact that I think it's unfair for advance ticket holders to receive a free reservation when others don't get it and indeed season ticket holders aren't permitted to make them at all. Perhaps make a seat reservation a supplementary charge with an advance.
I'm not aware of any TOC which charges to make a seat reservation. National Express tried it with East Coast and Greater Anglia- but only for walk-up tickets- but the new franchisees abolished the charges as soon as they could.
The problem with seat reservations is non-occupation. This is far more common with walk-up tickets than it is with Advance tickets, as on busy trains Advance ticket holders will take their reserved seat as that's the only one available. Repeated non-occupation is a big reason why TPE don't allow season ticket holders to reserve seats. It is/was not uncommon for season ticket holders to make reservations on several trains, and that's why it's been stopped. The justification for NX's charge for reservations was to discourage multiple reservations by walk-up ticket holders.
I'm not sure about ATW's solution because, unless they choose not to travel, you know the Advance ticket holder is going to be on the train that their reservation is for. Counted place reservations only save someone the hassle of putting the tickets out on the seats.