AtoBsafely
I had explained in that quote:
"I throttled back the Port engine until the exhaust was dark enough although still giving some power..."
Of course this would be at an inferior specific consumption of petrol on the Port engine. The Starboard remained at its normal cruising power, whatever that may have been ! (My Type Rating has lapsed, now.)
I had remained close to Blackpool aerodrome, which I see has just closed after over a century of use.
I spent most of my time on 4 engines with a F/E, so operating with one shut down was a part of life, sometimes.