And there's an enormous difference in importance between a sleepy route trundling across the IoW and a London tube line!
I'm 100% sure that a follow on order will happen, to immediately follow the 2024s on the production line. I imagine the Tories didn't want to provide funds before the Mayoral election and potentially give Sadiq credit, so it's either be done before the general election so that they can get some "levelling up" electoral benefit for the Goole plant, or it'll happen when the next government comes into power.