The version of Enbo translated by Desudesu isn't the 2008 one.

Check this description found in the English Hentai Blog:

Initially, Erotic Heart Mother was released in two volumes:

• Enbo (released in 1998)
• Zoku Enbo Futari (released in 1999)
  The first volume contained the first 6 chapters of the Erotic Heart Mother story and a few other unrelated short stories drawn by the same artist.
  The second volume contained the remaining chapters of Erotic Heart Mother (chapters 7 through 14 + Intermission + Epilogue) and, again, a few more unrelated short stories drawn by Miyabi Tsuzuru.

In January of 2004, a new manga was published (the one we've posted here), which contained only the chapters that were part of the Erotic Heart Mother story (all the other unrelated short stories were left out).
This version was probably released to accompany the 6 episode anime released between 2003 and 2004 (the anime was only about the main Erotic Heart Mother story, not the other ones).

In 2008, the (first) two books were republished for a compilation of Miyabi Tsuzuru's works (the new covers for Enbo and Zoku Enbo Futari).
These are the two books you're talking about. These are not sequels, just the same Erotic Heart Mother story with a few more short stories (which haven't been translated).

The original post has some links (check the 5th comment).

I think a modification is needed in the Enbo series, to clear everything up. Or, at least, a note with the above info.

If no one as other suggestions, I vote for putting the above quote in the "Description" field of the manga.