A quick look at the Oxford Shakespeare and the U Sydney indicates that each has one publication, albeit containing all or nearly all the principal Shakespeare works.

A difference at the Google site is that you can click on "all versions" and have a choice of many different publications of a given work.

As an example, clicking to "Merry Wives of Windsor" returns three pages of "choices" with 8 different editions (along with a couple of commentaries) on the first page.

Whether that's significant to a particular user is impossible for someone else to say. It has been my experience that a different "edition" can make quite a lot of difference in "readability," especially for some of the less quoted ones that may be a little less "standardized" by usage.

The copy of "Timon of Athens" that I found when I was about 9 y.o. after someone had tossed it under a neighbor's garage (© 1897) was pleasurable reading, but the "Bantam Books" version I had assigned as a college sophomore (©not quite that old) was brutal punishment. Of course maybe it was just the typography...

Others' experience may vary.

John