Freeing up space · Storage Profile, charts and Home
Why don't my big online-only cloud files show up in Biggest space-users?
Short answer: Online-only files take no space on your Mac until opened, and Biggest space-users ranks files by space actually used on disk, so they're left off. Downloaded cloud files do appear, with a Free up button.
Because they aren't using your disk. An online-only cloud file shows its full size in Finder, but takes no local space until you open it. Biggest space-users is measured by the space files actually use on this Mac's disk, so online-only files drop off the list.
What you see is the space you can genuinely reclaim, not a misleading total. Cloud files that are downloaded do appear, with a Free up button. See what Free up does.