The page https://www.nationalrail.co.uk/times_fares/ticket_types/Flexi-Season.aspx states:
It sounds like the various TOC smartcards are being made inter-compatible, presumably the first step towards one GBR smartcard. I wonder if this app will also later become the GBR app including other forms of ticketing.
How do you use a Flexi Season ticket?
Once you’ve purchased your Flexi Season ticket you will need to activate your day pass on the day you intend to travel by ‘touching in’ on the yellow reader on the gate, on the platform validator, or in some cases the self-service ticket machine. You can also activate it via the National Rail Smartcard app. More information about the National Rail Smartcard app will be available soon.
It sounds like the various TOC smartcards are being made inter-compatible, presumably the first step towards one GBR smartcard. I wonder if this app will also later become the GBR app including other forms of ticketing.