RAF fuel estimates and interservice budgeting culture

Why was the Royal Air Force honest about its fuel needs before the Second World War?

The tongue-in-cheek explanation is that it lacked the Navy's long budgeting experience and practiced creative accounting elsewhere.

The suggested explanation is that the prewar RAF lacked the Royal Navy's long experience of manipulating fuel estimates. It instead found room for creative accounting elsewhere. The comparison is a joke about service budgeting culture, with the Army and Navy portrayed as baffled by the RAF's unusually candid fuel figures.