XT M760 HT2 crank arm-stopper plate/spacer

I was putting my crank arm back on and noticed on the Shimano website that it mentions the use of what they refer to as a stopper plate,(a spacer)which fits in the slot on the arm between the 2 pinch bolts.
I don`t seem to have this,is it necessary?

Further research on the net has highlighted a m580 security plate.What does this do and does it matter if I ride the bike without it,until I can get anew one?
Though I am not sure it was fitted to begin with and I have had the chainset for 2 years………… 🙄

Dont worry about it. Its mainly there to make sure the LHS crank arm is on the axle enough. If its in the right place, a little pin in the plate slots into the small hole the axle.

I thought in the early versions they didn’t come with the plate? I have a set of XT cranks and they never came with them.