I think now we're venturing into a conversation of "perceived sweetness" which is immeasurable, but fun and interesting.
tannins, higher alcohol and bitter/sour will definitely subdue perceived sweetness. Oaking however, can actually work both ways - the tannins and char level in it can subdue perceived sweetness, but the vanillins can bump it up.
a 1.010 11% and a 1.010 15% technically are equally sweet by every objective means and methods of measurement, but the extra alcohol in the 15% abv beverage will mask your perception of the sweetness.
The trouble with your example, though, is that all the variables are all over the place - especially your yeast strains which have alcohol tolerances from 13% for the champagne, to 18% for the M05, so the numbers make sense and don't have anything to do with unfermentable - the m05 ravaged your sugars and ran out of them to metabolize, whereas, on the contrary, your champagne yeast probably hit its alcohol tolerance before it could finish metabolizing all of the sugars.
And if we get really into the weeds, there's the issue of atmospheric conditions such as temperature and altitude that can not only affect your physical measurements, but also perceived sweetness (cold and high altitude dull your taste). hell, even how much water you drank that day will affect your perception of how sweet something is.
And going even deeper into the realm of the unfermentable sugars rabbit hole, you'd have to take into account the differences in the unfermentable dextrins in honey versus unfermentable arabinose, rhamnose and xylose in wine grapes and adjust for their differences in sweetness. And even then, these quantities will vary between every single batch, because not only does every variety of honey and grape have different ratios of unfermentables, those quantities will change with each season based on climatic conditions - in reality, the minute variables are so complicated, it would be nearly impossible to make a pure and true 'apples to apples' comparison.
But the biggest wrench in the gear is that 'sweetness' measurements are actually subjective - the scale was derived from a panel of tasters, and their opinions of how sweet different sugars are (relative to sucrose being "1.0"), which was then tabulated and averaged into a consensus - there really isn't any 'true' scientific means or device to measure "real" sweetness.