The treaty counted battleships and battlecruisers together as one capital-ship category. This disadvantaged Britain and Japan, which already operated both types, while the United States had no battlecruisers in service. Once a navy must choose one limited set of capital ships, speed and battle-line strength become more attractive in the same hull, making the fast battleship a predictable result. The Queen Elizabeth class already pointed in that direction and might have reached roughly 27 to 28 knots with small-tube boilers.
Notable Point · 32:32-34:08
How one capital-ship category encouraged fast battleships
A single capital-ship category penalized fleets that operated both battleships and battlecruisers and encouraged the fast battleship, a type already foreshadowed by the Queen Elizabeth class.