Appreciate the explanation and link to the source file; makes sense.
However there is still a fundamental usability problem of the discoverability of how to file issues and suggested improvements for CSS module test suites.
I would like to suggest improving the generated test suite home pages themselves (e.g. http://test.csswg.org/suites/css-cascade-3_dev/nightly-unstable/) to link directly to https://github.com/w3c/web-platform-tests/ and suggest searching it for any source files one might want to file issues (or contribute patches) for, as you demonstrated in your comment (which I will do shortly for the cascade-import-002.htm source file specifically, thanks for the pointer. Update, done: https://github.com/w3c/web-platform-tests/issues/9910).
Note: the existing text of "More information on the contribution process and test guidelines is available on the wiki page." is not really useful, as the "wiki page" that is linked to (http://wiki.csswg.org/test) has A TON of links (a maze of passages that all appear alike if you will), none of which contain the precisely useful advice that you gave in your comment! Nor is it readily obvious how to fix http://wiki.csswg.org/test as it seems to serve many purposes, and the two likely links "How to Contribute" and "Reviewing Tests" both say on their pages: "This page has been deprecated and is no longer being maintained." with a top-level link to http://web-platform-tests.org/ which is also not useful, and that's already three clicks deep (if you guessed right which links to click) with still no answer as to how to contribute to this specific module's test suite.
Where should I file an issue and/or patch for the template or generation of the home pages of CSS module test suites like the specific page http://test.csswg.org/suites/css-cascade-3_dev/nightly-unstable/?