You’d be surprised how poorly developed systems for refund processing are at some TOCs. Note that the standard refund form hasn’t changed since BR days.
Some ask you to cut up a ticket that has clearly been marked by train staff though.
Edge cases. I have been asked to cut up a marked ticket when the delay was on the last part of the return leg - to the train’s final destination.
Maybe they assume you are a conjurer who's speciality is the 'cut up a banknote then miraculously put it back together ' illusion.
If they send that message to 100 people, I suspect a fair few would give up, especially on a ticket that’s only a few quid. I’m in no way suggesting they deliberately do this, but once you multiply those few quids by hundreds a week there’s certainly no incentive to prevent this from happening.
I've personally never had any issues with Greater Anglia (Abellio); indeed, on most occasions they've paid out within about 2 days!
As long as they don't threaten to prosecute you 12 months later!