I am not surprised that Northern get less (substantially less percentage wise if my understanding of the ORCATS process is correct) than even the lowest tier of their new Advances.
My surprise is with the claim that XC get so much more than Northern as to be classed as "enough" despite also only providing one journey opportunity an hour, unless I am reading too much into your comments.
Lots of flows are biased towards InterCity operators, regardless of actual service provision unless a specific flow has been queried/challenged.
The reality is that the ORCATs distribution factors for the majority of the UK flows haven't been reviewed since 1996.
But generally, if we were going to create a new allocation amount for LDS-YRK:
Northern run 1tph to York, and XC run 1tph to York, the reason XC should get a greater share is this:
1) Northern are running unattractive 2-car trains with far less capacity than modern, longer, more attractive services.
2) XC are running express services, the NT is more like a local service, and unless you are travelling to one of the intermediate stations, it is unlikely many people will be drawn to that service. People naturally want to be on the non-stopping service, even if that takes the same, or sometimes marginally more time to their destination. XC would normally carry more passengers per hour than Northern.
3) Northern price via Harrogate fares with 100% revenue allocation. These direct services to York can't really be said to create 2tph on the Any Permitted flow.
A lot of flows are set at simple percentage levels, like 50:50 just because nobody has really worked out actual demand.
Cornwall to South Wales flows are usually priced by ATW, but the ORCATS flow is 50:50 between FGW and XC only. Some flows use fixed £ amounts, some use fixed % amounts.
Software called MOIRA analyses specific flows, (on demand), and can see if additional stops or routes will be profitable for a TOC based on the timetable, passenger numbers, seating capacity etc that they input.
Bottom line is that ORCATs is largely left alone unless a TOC complains or an Open Access Operator wants to see what's in the pot. Some of the allocations are getting on to 20 years old without being unchanged since. Some TOCs are more proactive, some just focus on their 100% allocated flows and any other ORCATS revenue is just a bonus.