Some folks use "hull speed" generically, when they actually mean "maximum theoretical hull speed" -- aka 1.34 x SQRT(LWL).
Beebe makes a point that best economy is often down around 1.0x to 1.1x versus 1.34x.
FWIW, we found decent economy -- with our sorta-faster definitely-not-a-trawler by going "slow." Generally our slow cruise was more RPM-driven, not so much speedometer-driven. That usually meant anywhere between 7.5 (1.0x) and 8.5 kts, anywhere between 900-1200 RPM, depending on wind and current. We could approach 2 NMPG in best of circumstances, but it was more often in the neighborhood of 1.25-1.5 NMPG... while we enjoyed the coffee.
Chesapeake Bay, USA