Yes, I agree. This is a way I can go.
On the other hand, why not using a file sort order as default fallback, if there is no top-level HTML document available? Without any additional setting. Only a guess, because I believe, if there is an html-export, it will be organize for reading order mostly with a file order structure. Maybe Kovid can think about this some when in a future update.
The initial idea behind the request was, making an example using Calibre only. I did the import with an index.html, what include a very detailed ToC but w/o an explicit top-level HTML document.
I was surprised after I saw the result and my first thought was, I did something wrong.
