>the link is describing an 'upsized' noodle, not a parallel one
I disagree. Regardless, they are roughly equivalent, parallel being somewhat superior.
I regularly implement 200% neutrals as parallels of the same gage, e.g. #10 or #12.
I have never interpreted specifications for double neutrals as meaning that I should a single #6 instead, which would, I think, somewhat defeat the primary purpose, which is to haul away high frequency noise.