I have found the answer to actually be 'yes' you can release (flush) the VRAM. Here's what worked for me:
I have a hot corner (MacOS) set to turn the display off, and when I activate it, even just for a few moments, my GPU usage goes down to near zero once it comes back on -> not surprising since it’s off, BUT it continues to stay low as I go back to browsing around Chrome that stayed open, and other programs.
And keep in mind I’m pushing the VRAM with about 100 tabs open in Chrome that have many videos ready to play in the tabs.
So it seems the VRAM is released or flushed as the display is off but still remains low when using programs again. It’s almost as if it simply keeps things buffered as long as it thinks it needs it, which makes sense.
I often use large comps with big textures in Adobe After Effects, and that eats up all 16GB of VRAM no problem, so I know it’s there to be used, but the problem comes when I need AFX to use the GPU but it’s locked up in other apps where I can’t easily distinguish which one is using it.