I am pretty sure it's a tool state that cannot be relied upon. I discussed this with Google some time ago. While it does seem to work for some tools, it completely doesn't for others.
For instance, the line tool. State 1 might be a down and release of the LMB, and state 2 might be the second click to complete the line after you've moved the mouse. However, you can also down left click, move the mouse, and release the mouse to draw the line, in which case, the (hypothetical) state rule above does not apply.
The net of it all is that right now, we cannot depend on the tool state flag for anything, either because we don't have enough additional information to go along with it (like how the line tool is being used), or, it's simply residual information that is being push over through the API and is meaningless. (And that fact that "we're not supposed to be using it - it wasn't put in for us mere mortals")
Perhaps in the future it can be relied upon.
Todd
