Macs using the APFS file system are a bit more complicated in how storage is handled.
macOS utilizes APFS snapshots which may retain copies of data that has been emptied from the Trash. Usually these APFS snapshots are made by a backup utility such as the built-in macOS Time Machine backup software. Once a backup has been successfully transferred to external media, then the snapshot will be deleted from the boot drive. How long after I'm uncertain. If your backups have all been successfully transferred to external media, then you can try thinning or deleting an APFS snapshot.
View APFS snapshots in Disk Utility on Mac - Apple Support
https://derflounder.wordpress.com/2018/04/07/reclaiming-drive-space-by-thinning-apple-file-system-snapshot-backups/
Also, if you copy data to another location on the same APFS volume, then a second physical copy of the data is not created. Only a link to the same copy of the data is created which helps to provide more usable space. The problem is when you go to delete amount of data that was previously copied, then you are only deleting one link to the data. The data itself still remains on the drive since there is a second link to that "copied" data. It is hard to find an article which explains this in simple terms or even mentions it at all.
https://eshop.macsales.com/blog/43043-using-apfs-on-hdds-and-why-you-might-not-want-to/