Board Thread:General Discussion/@comment-18053181-20141214100556/@comment-6697950-20141214102212

The author actually treats Progressive as canon so far. Of course he retconned some things, but the later novels in the main series and latest side stories have begun referencing the events in Progressive.

The original series is actually fully written as a web novel, just that the web novel is still not fully published as a light novel. The author is only making small scale changes to the web version before it is published, so he's not really continuing to write the main series as you are implying.

And the motivation for writing Progressive possibly came from the fact that the fans enjoyed the Aincrad arc, but didn't enjoy the timeskips much, so Progressive covers the Aincrad arc floor by floor instead of using time skips.