Please don't defer that Manage Authors step - do it now. We listed it as the next step for a reason
As I said above there is a default sort for your authors, and if you don't go into Manage Authors and make sure your default is correct (and at the same time take advantage of fixing the display author for all your books) then you will likely end up with some quirky results, which will have you puzzling even more. Fix that now, and then worry about the new books.
As for why calibre does not have such a feature, it is because calibre has no concept of author last names. And there are geunine international reasons for this - while it is perfectly acceptable for us to just flip around the last word of an english name so "Joe Bloggs" becomes "Bloggs, Joe" which is what the QC plugin does, that doesn't work for other multinational names. Like "Kim Lee" where Kim is the family name and the correct reversal would be "Kim, Lee" not "Lee, Kim".
When I said regular expression I meant whatever your settings are in Preferences -> Adding Books. If you have "Get metadata from filename" ticked, then the author name will come from what is embedded in the metadat for that book format when you add it, as specified by the publisher of that book. You have zero control over what that is - sometimes it might be "FN LN", sometimes it is "LN, FN" and sometimes it isn't even the authors name and is the book title or something else.
Alternatively you can uncheck that "Read metadata" option and rely on the filename. Which is where the regular expression comes in. Now this only works if your filenames are in a consistent format - like "Author - Title.epub" or whatever. In that situation if your book files happened to be actually named "LN, FN - Title.epub" for instance, then calibre will have the author as LN, FN for you which is what I meant above. If your books are randomly or inconsistently named, it won't help you.
And you also have the complication of downloading metadata, and making sure you have the "Swap author names from FN LN to LN, FN" option checked if you are overwriting the Authors field.
Bottom line - I find the easiest way is to drag/drop the books into calibre, look at the author field and if it needs swapping to LN, FN then just use the QC plugins "Fix" menu to swap it for you. Or manually edit it. Then make sure you have your metadata download configured to either ignore the authors field, or to swap author names as I said above. Then you should be fine.