Not quite sure I understand exactly what you're getting at? Are you wondering if those constraints are less important because you less frequently order by UUIDs

Not quite sure I understand exactly what you're getting at? Are you wondering if those constraints are less important because you less frequently order by UUIDs? If so, I don't think it makes a huge difference - merge joins are still relevant, and you'll often ORDER BY anyway just to get stable resultsets. If the question is if there's bigger benefits to hash joins for largely unordered data? Then yes, that's true.