That would be because an an ‘any time’ return from the East Coast site is £239, booking in advance it was £90.
Yep, and the trade off for that is that you have to go on that booked train!
I suspect it’s often the case on flights as well, but if I booked a bargain fair with EasyJet I’d not expect them to transfer me to another flight just because I turned up earlier (when that’s specifically in the T&Cs that they won’t).
Just saying like, why should they bend the rules for you?
But yes, DOR who run East Coast are making a bigger hash of it than NX did, which is slightly ironic. Who wants BR back!?