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The entire crux of this debate is about reducing the noise in an image.
Noise comes from various sources including (but not limited to) dark noise, read noise, random noise, cosmic rays etc.
The important 2 here are probably read noise and dark noise and it depends which is more prevalent in the exposure.
For short exposures the read noise becomes greater than the dark noise so subtracting a dark that has inherent read noise in it may actually increase the noise in the image. This is when just using an offset for the flat frames is of benefit.
You can reduce the read noise by averaging large numbers of dark frames or bias frames before subtracting them. This is where ICNR falls down for short exposures (and probably why the cameras don't allow it below a certain exposure time.)
If the flat frame exposure is long enough that the dark current is the dominant source of noise then the subtraction of a dark will help.
In the end for non science images it probably doesn't make a lot of difference.
I've attached an article about the detection of exoplanet transits using amateur equipment. It has a very nice explanation of the sources of noise in images.
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