S&W M&P and the sear deactivation lever.

[FullEffect1911]

I have a question regarding the sear deactivation lever on the M&P series of pistols. Upon reassembly from field stripping the instructions indicate that the sear deactivation lever is supposed to be in the down (deactivated) position when the pistol is reassembled. Why? I know for a fact that the pistol will reassemble whether the lever is up or down, so why the extra instruction in the manual? Is something being damaged with it being in the up position?

For the record I have a recent manufacture of M&P and the tip of the sear deactivation lever is straight.