Why faster British battleships would not change treaty ratios

Could faster British battleships justify Japanese completion of Tosa and Amagi under a treaty?

Probably not, because the negotiations were framed around battle-fleet firepower rather than speed.

Faster Queen Elizabeth and R-class ships would improve British operational capability without directly increasing their counted gun power. Britain deliberately framed the negotiations around firepower rather than battle-line speed. That choice denied Japan and the United States an easy claim that faster British ships justified more new construction. Arms-control arithmetic can privilege selected measures while leaving important combat qualities outside the headline ratio.