Mac external Disk full but not the case when you check the content

I have spent the last 2 days trying to gain space for my MAC internal SSD due to iCloud wanting to download files all the time even with optimise iCloud storage ticked. Optimise should make disk utilisation better through an automation algorithm but my experience along with many others would suggest it does what it wants when it wants. It certainly appeared to remove disk space management from my grasp. To my horror my internal disk free space was disappearing fast until it reduced to less than 2% of the available space. I needed to find a big external drive so I could move my iCloud data.

I started deleting old files and folders on the external drive but the free space wasn't reclaimed. Both Disk Utility and finder reported the space incorrectly and by a huge margin after adding up all known folders it was out by more than 60%. I tried emptying the trash bin again as the same user on the same Mac and running first aid in safe mode - all to no avail.

I suspected that the issue was related to the deleted files not being fully removed. After lots of reading forums I discovered that there are hidden files on the disks and these could be displayed by Command + Shift + period ie (.) This allowed me to see the thousands of files under a hidden folder named Trashes. Contrary to differing expert advice I deleted the contents which fixed my issue instantly. I can't believe that it took me so long to find this hidden (ironic) solution and wanted to share this with you all so you don't have to waist days like me.

My question is "Why doesn't Emptying the Trash get rid of the files in the first place to avoid a cloak and dagger approach to disk management"?