Did Britain simply fudge the naval treaty figures in its favor?
Short answerThe deeper advantage was that Britain helped write definitions such as standard displacement, which already suited British construction and operating practice.
NotesA joking question about Britain fudging figures opens a more useful point about rulemaking power. Britain frequently helped write the naval treaty definitions under which fleets were compared. Standard displacement and related regulations aligned well with the way the Royal Navy already designed and operated ships. Shaping a common framework around existing national practice offered a greater advantage than simply misreporting numbers after the rules were set.