It appears that ATW expect you to buy a ticket at the first available opportunity. If that causes you to miss your train then so be it. In stations where there are barriers you must have a ticket or you can't even get to the platform. I'm not suggesting I agree with ATW. It's natural to want to get on the first train that arrives, especially if you've been delayed you need to get to work, an appointment etc on time. ATW are more concerned for their revenue than getting you to your destination on time.
In cases where people alight at stations with barriers and have to buy tickets anyway, this heavy handed approach is simply about revenue - paying for the green jacket brigade probably. In the valleys where few, if any, stations have barriers, you never see them about waiting for the little shits who hide in toilets going a station or two along the line. They're always looking for supposed "fare dodgers" where passengers have little opportunity to actually dodge fares.