For a framework it might be a nicer option, so that you can drop a module by only deleting the include reference rather than permanently deleting dozens of lines. Perhaps. It’s largely down to taste I imagine :)
I recently used a bastardisation of v3 and v4 (I was using v3 then you released v4) and I split each object into separate files and left the imports commented out in the main.scss file.
I then uncommented each object as I used it so I didn't reach the end of the project with unused objects in the CSS and not being able to remember whether or not I had actually used them.
I did a similar thing with the grid module: commented out all sizes and uncommented what I used as I went.
