gmatzpractice great question! The Official Guide doesn't include too many 700+ level problems, but there are some in there. This post was specifically referring to the new content in the OG 2019. In our rating system, we aim for a curve that matches the GMAT score thresholds. So an average problem that we score as a 5 would be roughly the kind of problem that a 550 level scorer should be answering correctly. For more advanced content, we partner with
Magoosh so that all of our students have access to
Magoosh's question bank, which has many more advanced level questions. Also, the official supplemental guide has more advanced problems.
So I would say that the Official Guide provides plenty of material for test takers looking to score in the 600-650 range, but those who are aiming higher should seek some more advanced content in either the supplemental guides or third-party sites.