I cannot convince a non-aircrew colleague of mine that on large supercharged piston engines with constant-speed-propellers, if you lost an engine during cruise due to fuel starvation, it would continue to windmill at the selected rpm with accompanying boost (manifold pressure) and oil pressure.
It is not surprising that you cannot convince a non-aircrew colleague, because, your information is incorrect....in so far as the following engines are concerned:
Pratt&Whitney R2000, R2800CB16, R4360...CurtisWright R3350 turbocompound series.
Yes,the RPM remains the same (in your selected scenario), the oil pressure (usually) remains OK, however, the manifold pressure and BMEP are most definitely reduced when the fuel flow ceases due to fuel exhaustion.
And yes,I've flown all of the above types on a variety of aircraft, IE: DC4, DC6, DC7, 1649 Constellation, Stratocruiser (B377).