Yes, you don’t exactly need to know what queries will look like, but I don’t think the GP claimed that.

You need to have a fairly detailed knowledge, though. How are you going to make educated trade-offs if you don’t know what kind of queries will be made, how often, and how important it is they run fast?

That’s why, in evolving programs, the database evolves, too, even if the table content stays 100% the same. Moving some tables to faster storage, splitting them horizontally or vertically, adding or removing indices, compressing or no longer compressing fields, updating statistics more frequently, etc.