Agree, Chris. This sort of nonsense needs stamping out very quickly.
I take it this "nonsense" is one of the measures to reduce the risk of catching COVID on a train where social distancing isn't possible due to overcrowding?
If it is, then it's a half hearted measure. People can still buy walk up tickets from ticket offices and
TVMs▸ without restriction.
Also, I've just checked the old Mixing Deck booking engine (tickets.gwr.com), and the Android app, and neither of those appear to be restricting the sale of walk up tickets for trains in the next few hours, or in the evening peak from Paddington.