Huh? My Pale Moon is at 780 MB when that page is opened along with this forum, one short thread on old Reddit, another forum and a video playing on YouTube (using PROJECT VORAPIS frontend). Maybe everything on Windows just shows as using more memory if it's available? Or do you have millions extensions in both browsers? I have 6 GB of RAM total.
Idle consumption does seems to indicate like it could matter, but I'm not 100% certain as my only other reference is work laptop with 12 GB of RAM which I haven't setup myself from scratch.
Though that Pale Moon's reading I took is from Lubuntu 20.04, I'll check Windows 10 later, though I don't expect it to be much different.