Duplicate files · Choosing which copy to keep
Why are some identical files listed as freeing no space?
Short answer: Some identical files share the same storage on disk — APFS clones made by duplicating in Finder, or hard links — so removing one frees nothing. Storage Studio shows them in a separate "reclaims no space" section and never removes them.
Some files look like separate copies but actually share the same storage on your disk. On Macs with the APFS file system, duplicating a file in Finder often creates a clone that takes no extra space until one copy is changed; hard links are two names for the very same file.
Removing one of those wouldn't give you any space back, so Storage Studio lists them in a separate section — "Identical, but freeing these reclaims no space" — and never removes them. If you try, you'll see "These copies share storage, so removing them wouldn't free space."
This is also why a set's "to free" figure can be smaller than the files' sizes suggest.