" it also seems that dwarven inability to allocate build points to Arcane also doesn’t seem to have any effect on the calculation of the racial XP costs but is a significant, noteworthy deviation from baseline. I would say it “should” affect the XP value of the Dwarf."
Should that really affect the XP value for Dwarf, though? Should playing a fightery dwarf cost more XP because some other dwarf could hypothetically be a wizard? XP-to-level should charge you for the abilities you actually get, rather than what some other class that happens to be the same race could have gotten. If the concern is that the dwarf save bonuses are too good when you apply them to the Arcane base saves, that’s one thing, but the sensible solution to that is “change dwarf save bonuses if using the Arcane save progression”, rather than “penalize all dwarves everywhere by raising the XP cost.” Similar approaches ought to apply for pretty much all other sources of dwarf+arcane mechanical incompatibility (assuming there are in fact any, and that it’s not purely a flavor restriction).