Yes, you could "split" at Hartlepool instead, that will reduce the price further by around £8. (As I am sure you're aware, the train would need to call at Hartlepool, and you could take the Metro or Northern to Sunderland and take GC from there, or change at Thornaby/Middlesbrough)
As for anomalies, not really, though about 5 years ago you could have got a Newcastle - Carlisle and finished "short" at York as this used to be a permitted route. It ceased to be a permitted route when the brother of a forum member was challenged on this ticket and incorrectly charged a new ticket by the guard, he then successfully appealed the cost of the new ticket, but the Routeing Guide was changed a few months later (though not with permission or knowledge of the DfT so it would appear to have been an illegal change, hmm!). However, we do not advertise that sort of anomaly, for fairly obvious reasons. It would unlikely to have been a stress-free journey. The problem with using anomalies is that you can encounter problems if it is not accepted/honoured, and they are subject to withdrawal if they are brought to the attention of the TOCs.
