The F3 design and an all-15-inch Royal Navy battlefleet

What would have persuaded the Royal Navy to adopt an all-15-inch battlefleet during the 1922 treaty negotiations instead of Nelson and Rodney?

A greater need to match fast American and Japanese ships could have favored the more balanced F3 concept, armed with 15-inch/50 guns rather than the older 15-inch/42.

The Royal Navy considered both 15-inch and 16-inch paths before choosing the Nelson design. If American and Japanese capital ships appeared fast enough to demand a quicker response, the navy might have favored the F3 concept's more even balance of speed, armor, and firepower. The weapon would not simply be the old 15-inch/42; the alternative fleet would use a 15-inch/50 gun. The perceived speed of foreign ships could shift a treaty design away from maximum firepower toward a more balanced capital ship.