After emptying Trash, the available space on my MBP SSD doesn't change
I have a MacBook Pro (15-inch, 2017) with a 1TB SSD, and when I empty the Trash (usually >5GB at a time), the space available as reported in the Finder as well as in the Manage Storage pane *doesn't change*, however the "System" size *continues to increase*.
For example, just now, before deleting about 57.6GB from my Trash, my available space was about 575GB. But after emptying the trash, the available space is showing 572.4GB.
Can someone confirm to me that this is a normal function of the SSD, and that reclaimed space available on the SSD is only released as the remaining available space gets lower?? I seem to remember reading that somewhere a while back, but can't find any confirmation of it.
If this is normal, so be it. But I can't seem to find any information about this behavior.
This is a Manage Storage screenshot after the above-mentioned Trash deletion.
MacBook Pro 15", macOS 10.14