IMHO it's completely unnecessary. A piece of MDF with some sand paper glued to it is all you need to flatten out a saddle. I realize I might sound like a jerk saying that and I don't mean too. I love Stew Mac don't get me wrong but sometimes they just way over think things. Jigs are great for eliminating guess work and standardizing a process so I guess it's good for that. But it's not something that is too difficult to do. You could even make a very simple shooting board out of a scrap block of wood that you square up perfectly.
As for thinning a saddle check out this little jig on Frank Fords site.
http://www.frets.com/FretsPages/Luth...saddlepal.html