The answer is that user-agents (from what i know, to date, at least) is that they all handle css style sheet imports using the "@import url(file.css)" the same way....
They ignore them, They don't download them when saving the web page. It's a bit of a negative feature. But it's the way they all work. Some people especially web page designers really like this features as it discourages stealing of web page designs....
Yet, don't loose hope, you can use the older and very much still supported alternate, instead: