Bug, feature request, or proposal:

Bug? Proposal?

What is the current behavior?

In the output _theming.scss, there is massive duplication of the palettes and mixins.

The 756 KB file can be brought down to ~82 KB by removing the duplication.

What is the use-case or motivation for changing an existing behavior?

I don't really know/understand how big of deal this is. I guess it slows down npm download times and takes up 600 KB+ more disk space than required.

Related to #3776