Why Japan struggled to reach the fast-battleship threshold

Why did Japan struggle to produce a true fast battleship when Queen Elizabeth could have reached 28 knots with small-tube boilers?

Japan had useful early ideas, but the construction pause eroded experience; later ships such as Yamato did not meet the 28-knot cruiser-line threshold.

The answer uses 28 knots as the fast-battleship threshold because the ship must maintain contact with the cruiser line. On that definition, Yamato's 27 knots fall short, however small the numerical gap appears. The cruiser-line requirement is traced to about 1912-1913. The Queen Elizabeth comparison depends on an efficient hull and the hypothetical use of small-tube boilers. Japan is credited with promising earlier ideas, but the construction pause interrupted the institutional experience built up in the 1910s. That loss of continuity is offered as the explanation for later difficulty turning those ideas into faster ships.