The backset sour mash myth?

[S-Cackalacky]

The title - just being facetious.

I may get burned for this, but it's something I've wondered about for some time. The addition of backset to a grain sugarhead like UJSSM or SF seems to be considered a necessary step to creating a sour mash (wash) ferment. I'm making this post to try to find out if this is indeed the consensus among the members here.

I've always believed that the souring of the mash is a result of reusing the lees left in the fermenter along with the action of some naturally present bacteria. There are even topics here on the forums outlining procedures for develping a sour mash starter using a cracked corn/sugar/water mix. I also believe that the backset addition to subsequent ferments is basically a flavor enhancer and nothing more.

Am I correct in these assumptions, or is the backset really a necessary component in the production of a sour mash? And if so, what's the science behind it?

It's just that I keep hearing over and over that backset is a necessary component of a sour mash and don't really understand why that is. I promise I won't get pissed if contradicted - just looking for the facts.