Do Shimano disc brakes need post mount spacers? I am switching my rear Avid Elixir brake for a Shimano XT one, but I am a bit unsure about mounting the caliper. The Avid brakes had spacers that put the brakes in the right position for the 160 mm rotor I am using, but the Shimano ones do not come with any spacers. The Shimano manual says to mount the caliper directly to the post mounts, without any further explanation for different rotor sizes. So is mounting the caliper directly to the post mounts correct for a 160 mm rotor, or do I need any spacers as with the Avid brake?
If your fork is a post mount, and your rotor is 160mm, you will not need additional adapters or spacers to fit a Shimano brake.  The image from the manual you posted is correct.