This seems to be connected to FileVault. If the volume is FileVault-encrypted, it can get quite “greedy” about holding onto deleted files.
Even though it is supposed to let go of the space upon demand, it is my experience that it does not.
When a big update came out (don’t remember exactly which one, but it was a couple or so months ago), my disk space was down to about 13GB free, even though I had deleted over 150GB of files. The update refused to run, citing lack of space.
I had to wipe the disk, and use Migration Assistant to restore the disk.
That was the second time this has happened.
I think that this particular aspect of APFS still needs a lot of work.
Even though it is supposed to let go of the space upon demand, it is my experience that it does not.
When a big update came out (don’t remember exactly which one, but it was a couple or so months ago), my disk space was down to about 13GB free, even though I had deleted over 150GB of files. The update refused to run, citing lack of space.
I had to wipe the disk, and use Migration Assistant to restore the disk.
That was the second time this has happened.
I think that this particular aspect of APFS still needs a lot of work.