I was curious myself. I dug up the original proposal to create sjavac, which is here: http://openjdk.java.net/jeps/139
Interesting -- finally bringing multiple-core/process compiling to javac. Although, I must admit, I have yet to work on a project where compile times were a major issue. I guess I'm just in the habit of typing "ant release" and getting some coffee ;)
It's unclear if you are poking fun, but one of the major features of Eclipse (and ejc, by extension) is the "compile on save", so there is no compilation step while working in your IDE (unless, of course, you desired one).
If that is a goal of the sjavac project, then the ability to compile in parallel the different branches of the dependency tree for a set of classes would make for a major upgrade in user experience.
(link provides no real details: http://openjdk.java.net/jeps/199)