The automatic boost control cut out was intended as a emergency measure in case of automatic boost control failure, as 41Sqn_Banks post already indicated. This would be valid independent of fuel used. The procedure would be to cut the throttle, activate the cut out, and reopen throttle until the desired boost is reached. From then on, changes in speed and altitude would cause a change in boost, which could be controlled by change of throttle or engine rpm (supercharger rpm).
The use of as an emergency boost increase was a later practice. However, unless a report makes specific mention of abc failure, there's absolutely no reason to believe it was activated for anything but a 12lbs emergency boost any time 1940 or later.
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