Worksession still slow in V8 + file size "mystery"

Using V8 SR7, I’m still finding that Worksessions are sluggish to the point of being unusable.
I try to use them to get large textured photogrammetry meshes or point clouds in my work model, as a reference, without having to save these very heavy assets every time I save my file.
The first issue is that if you want to de-attach one of these files, you can either call the Worksession manager or right-click on the layer that represents the file, but that puts Rhino in a coma, roughly proportionnal to the size of the file.

I don’t get it. This is like if I had to lift the elevator instead of riding it…

Now it gets more interesting : If I save my 24 MB work file while having a large attached file, it suddenly weighs over 500 MB which (surprise-surprise ! ) is similar to the weight of the attached file.
Then if I close the work file and re-open it, it still weighs 500 MB…until I save it again, and it’s back to 24 MB.

I think of Worksessions as a SolidWorks assembly. You’re just referencing a bunch of file in a “Master” file, and you can make any one of the part files “current”, and that’s great.
But if SolidWorks managed the data in memory and on drives like Rhino, if would not be so successful.

There is an existing youtrack (private), the textures aren’t being cached properly. I believe there fix will be available soon.