Why turbines define a true dreadnought

Which early American battleships count as true dreadnoughts if some retained vertical triple-expansion engines?

Turbine-powered USS North Dakota is the first true American dreadnought under this definition because turbine power density, rather than a 21-knot dash alone, was central to Dreadnought's generational change.

The answer treats turbines as a defining part of the dreadnought package. Vertical triple-expansion machinery might produce a short high-speed dash, but turbines made that performance more sustainable. The greater power density also helped transform hull layout, armor, size, and overall ship form. Vertical triple-expansion ships may still be called dreadnoughts for convenience, but North Dakota becomes the clearer American starting point under this stricter definition.