Obviously though if you further delay yourself by choice Delay Repay is arguably only payable based on the shortest delay you could have incurred, unless you physically could not board that next train. You can't claim an hour just because you were 397 bashing and didn't want a Pendolino in half an hour. Of course this is one reason to do this - it will save the railway money!
The trouble with trying to enforce that principle is delay repay software will just look for and find the optimum route and assume a passenger intending to take a different route would have known they should take it. That's unreasonable.
The route that turns out to be quickest and the route that journey planners would have told you to take if you ran a search at the time when the passenger had to make the decision, may be two entirely different routes. Passengers who act reasonably to try to mitigate their delay but end up choosing a sub-optimal route shouldn't be penalised.
It is still advantageous to open up alternative routes for passengers. It will often help them mitigate their delay.
Even if it doesn't, it can still be worthwhile. I was once at Euston when the WCML suddenly had to close and the usual chaos ensued. We were advised to go to Kings Cross and divert. When I checked later, it would in theory have been 20 minutes faster to wait it out at Euston than to divert via Kings Cross and Doncaster as I did, but only if I had managed to get on the first northbound train to run once the line re-opened. I've no idea if it would have been possible to board that train, but I am sure it was better and more comfortable for me, and better operationally for Network Rail (in terms of maintaining safe conditions at Euston) and for Avanti that I didn't try.
