I might be the only one here, but the idea of Standard Premium really frustrates me. I like travelling first class for the food and drink - even if it is just a sandwhich and drinks. As I usually travel long distance at unsociable hours many shops etc aren’t open, so I’d rather pay £10-15 to upgrade to first class (via Seatfrog) and know I’m going to get food plus several rounds of drinks. I don’t mind the seats in standard so I’m not upgrading for a better seat.
Seatfrog, to be fair, is selling unsold seats at very low prices. It's to your advantage, but it means the class is not working because the seats are not being sold at a price more related to their value. When you consider that First Class seats take up about 1.5 times the space Standard ones do, that makes that multiplier sensible for the basic product - if you add freebies on top they are heading towards it potentially even being a loss leader.
Everyone loves a bargain, but a viable business doesn't exist if almost everything is being sold that way.
I think this sort of sits with "rail enthusiasts are frustrated that fares are to be simplified because it means they won't be able to get a bargain due to their inside knowledge" - yes, that is a bit annoying if you've become an expert, but the overall benefit of a simpler system is significant.
But yes, I'm with the other poster - if you're spending £10-15 and don't care about the seat, spend it on food to take with you (cheaper and better range than on-board) and just buy teas or coffees if you want those, and sit in Standard - and avoid faffing with apps! (I guess for you the other possible model would work - First Class service with a Standard style seat - i.e. BR "Silver Standard").
Personally the thing that's important to me is the wider seat (ideally on the 1 side) and enough space to use a laptop. I assume they must have done surveys to see which worked best, as something like Voyager "Coach D" but with service (2+2 but all tables etc) might also have been an option.