shims from rear pivot shaft

The information given is not a typo . . . and is stated directly within the Yamaha TD2/3 (model 240) service manual. I'm not able to say if Yamaha made an error, but I don't believe so.

It's not a cosmetic part, and the Yamaha engineers that designed these bikes seem to think it was necessary, as they continued to use these shims on many models, and for many years. I supplied you with the information you asked for, but I don't feel comfortable commenting on how you should proceed.