I‘be always interpreted that as a visibility issue. You have to be able to see the ground or water - if there is something to see. It’s not to be able to discern the ground or water.
Exactly, there can be occasions flying day VMC where you can be confronted with exactly the same situation as you are with NVMC. Two examples, one of which
CS would probably be more than familiar with.
Took a ride to Antarctica with QF and at one point the crew pointed out the phenomena of "whiteout", something they made a point of as it was post the Erebus crash, we were flying beneath an 18,000' overcast and over featureless all white (snow) terrain with unlimited visibility, no matter where you looked it was the same all white colour, you were at the centre of a sphere with the exact same colour to be seen no matter the direction you looked. We had the terrain in sight as the regs require, but there was nothing to "see", that would have required something to provide contrast. Oh, and no horizon to be seen.
Flying off shore in my day job during a period of massive bushfires which had left a pall of smoke from sea level to 10,000' over the ocean, ocean was like a mill pond, not a ripple, no cloud, visibility well in excess of VMC minima, but no matter which direction you looked, up, down, sideways, it was all the same bluish/grey colour, once again we were at the centre of that sphere. The ocean was in sight as called for by the regs once again, but there was nothing to provide the necessary contrast for you to "see". Once again, no horizon.
In both cases you have ticked every box to meet the VMC requirements, just as you have on a pitch black night, the ground/water is in sight but because it's night there is nothing to provide contrast for you to "see". but if you don't have solid IMC skills you'll be up the proverbial creek without a paddle. How long do they say for an untrained pilot to lose control upon entering IMC, about thirty seconds I seem to recall.
What do you say about the operational requirement in row 4 of Table 2.07 of the
Part 91 MOS? Is it applicable to NVFR flights in aircraft in G at or below whichever is the higher of 3,000’ AMSL and 1,000’ AGL? If yes, what does it require in substance?
The table says
Aircraft must be operated in sight of ground or water
You are doing just that, operating in sight of the ground or water, but because of the lack of contrast there is nothing to "see". I think you're over thinking the problem
Clinton, IMHO.
Be careful out there, fly safe, be mindful of your skill and proficiency.