Honestly, it makes sense, given the how the 2024 PHB presents orcs. It would be completely reasonable to have a homeland where orcs of every alignment could be from. And that area is rough and hardly mapped - there's plenty of room in the Spine of the World and the Ice Spires between the scattered dwarf settlements in old Luruar and Hartsvale to the northeast for a remnant kingdom to still be around. It would very easy to add in some "hitherto unmapped valleys" in that region, as it's very hostile climatically and geographically for explorers to visit.