A.P. 129 RAF Flying Training Manual, Part I - Landplanes

[Crumpp]

combat reports that mention the use of boost control cut-out are not a proof for 100 octane fuel.

That is correct.

According to the RAF, the pilot could use boost cut out to achieve more power under any circumstances he felt balanced his risk.

Therefore, you will see it's use and it not surprising at all that running the engine at such an overloaded condition got attention from Dowding.