It's a national rail condition of travel that you buy a ticket before travelling, wherever possible - that means if there is a ticket office or vending machine at the start of your journey OR you have a smart phone, you can be fined if you travel without a ticket - that is national and has pretty much always been the case (not the smart phone bit, but as 80% of rail tickets are bought online, they do now expect you to do this before boarding the train).
Lots of people on this thread have said they have bought tickets on the train before/have regularly seen this happen, and it does happen but unfortunately rail operators and the DfT are now starting to crack down on this and issuing fines where they would previously just sell you a ticket. I'm seeing more often that conductors are not even being allowed to take a ticket machine on board with them, they are only able to give out fines, and this is going to keep happening - it is one of (the MANY) reasons that rail staff are still on strike.
Basically the thinking behind it, is that firstly, you will get less fare dodgers/chancers who only pay once in a blue moon, as soon it will be a case of buy a ticket before travelling or get a fine, there will be no way to buy one on the train. Then, once a situation is created where noone is travelling without a ticket, or conductors aren't selling any tickets anymore, it is just another reason why a conductor is no longer needed on a train, and takes us another step closer to the DfT being able to force through plans to remove conductors from trains.
In this situation though OP, it does sound like the conductor was an arse to your DD, I expect that was at least in part because he is sick of being forced to hand out these stupid fucking fines and was more than happy to accept a false name and address because he knows they are bullshit.
All that to say, noone is going to come chasing your DD about this - but I would urge anyone on here who says they regularly buy a ticket on board the train to start buying before you travel, you don't have to wait at long queues if you download one of the many apps that let you buy tickets, because this will be happening all over the UK sooner or later, and you won't get any warning, you'll just be told it is part of the conditions of travel and always has been.
A few of the train companies have recently been doing disability impact surveys around this and closing of ticket offices, so if you do feel strongly about the impact, some of them may still be open and you can voice your concerns.
(sorry OP, this isn't really an answer to your question, but just wanted to spread this info for anyone who doesn't know)