You can roll your eyes, but @Bletchleyite is right. There's only a fixed pot of money so it should be spent where it gives maximum benefit. Where transportation safety is concerned the priority should be on road interventions because roads are much more dangerous than railways. In 11 of the last 12 years there have been 10 or fewer passenger fatalities on the mainline railway. As compared to over 1,7000 road fatalities in each of those years.*rolls eyes*
The money that would be spent replacing the HSTs five years early would be much better spent fixing deficiencies in the road network.
There's a case for replacing the HSTs because they're more expensive to operate, because they put out a lot more CO2, because they aren't as reliable or aren't as accessible as a new fleet would be, but there's no case to be made on the grounds of safety. At least not until the RAIB or similar reports that they are objectively unsafe.