It's probably the bit where it says "...can only be used on Arriva Trains Wales services..." that is a giveaway...
I only ask because ATW got other TOCs to sign the PIF for that product and we all signed, including FGW...
FGW are getting revenue from that ticket sale through ORCATS, regardless what discount is applied. The railcard itself doesn't say valid only on ATW as far as I can tell, and the tickets are routed Any Permitted. The Manual entry does not mention a restriction.
It wouldn't comply with Condition 10 NRCoC if it restricted the holder to ATW services.
All of this combined, I would really advise you to speak to Mr Pritchard to clarify FGW position.
Certainly the Pembrokshire/Senior Valleys Railcard and Ticket to Ride are definitely inter-available.
Why would just 1 of the entire range of Welsh railcard prohibit other TOCs?