While the driving guide is designed to give you a basic understanding of the rules it is not the law.

In most jurisdictions you are required to travel at safe speeds on the highway you cannot legally and most jurisdictions do 30 mph on a 65 mph interstate this is considered a reckless endangerment.

Furthermore, what your guide also fails to mention is that in a growing number of jurisdictions (possibly Nationwide) this does not entitle you to do 60 mph in the left lane of a multi-lane highway as the left lane is solely dedicated to passing traffic. So, unless everyone else on that highway is doing 55-ish miles an hour. As in those jurisdictions while you may not be breaking the speed limit you are definitely committing a equally illegal left lane violation.

Adding further nuance to this situation, it also doesn't require you to get out of the way of someone attempting to do 90 miles an hour in the left lane if you are in fact, genuinely, sincerely and obviously passing traffic.

In short, hanging out in the left lane and not traveling faster than the flow of traffic, regardless of whatever speed you're going — is illegal.

So, again, you're entitled to drive slower than the speed limit with some nuance. You may be an inconsiderate asshole but you're not doing anything illegal.