In more practical terms:-

1. Users - your users table may not benefit by being ordered by created_at ( or uuid7 ) index because whether or not you need to query that data is tied to the users activity rather than when they first on-boarded.

2 Orders - The majority of your queries on recent orders or historical reporting type query which should benefit for a created_at ( or uuidv7 ) index.

Obviously the argument is then you're leaking data in the key, but my personal take is this is over stated. You might not want to tell people how old a User is, but you're pretty much always going to tell them how old an Order is.