The proposed classification requires at least 28 knots together with battleship-grade armour coverage and subdivision for a fast battleship. Yamato's 27 knots leaves her a very large conventional battleship, while the 28-knot King George V class clears the speed threshold. Reductions in armour coverage and subdivision move a design toward the battlecruiser side of the taxonomy. Torpedo protection is not a clean dividing line because treaty-era designs often compromised it while later designs generally improved it.
Notable Point · 55:45-57:39
Why Yamato is not a fast battleship in this framework
A proposed speed-and-protection classification places 27-knot Yamato below the 28-knot fast-battleship threshold.