Which attachment? 

This one — 
https://www.sonos.com/en-us/shop/sanus-tv-mount-beam

I am guessing they are referring to this?  There is more information here from Sanus.

From what I can tell, it’s not just a matter of working with the TV, but with the TV mount you’re using.  This will go between the TV and your TV wall mount hardware.  Look through the PDF instructions and you get a pretty good idea of how it works.  If you don’t have an existing wall mount, then I would get a Sanus wall mount to match this.  If not, it should be ok with any wall mount that isn’t out of the ordinary.