Role Hierarchy and Performance During Massive Load of Portal Accounts

In the trailhead module Large Data Volumes it says 

Role hierarchy. You might think that loading would be faster if the owners of your records were not members of the role hierarchy. But in almost all cases, the performance would be the same, and it would be considerably faster if you were loading portal accounts. So there’s no benefit to deferring this aspect of configuration.

So I’m confused whether it is faster to load portal accounts with owners in the role hierarchy or not.