That  only happens if you try to change the refresh rate for the 767-300ER PW4060 4D model.

Contents of the 767-300ER PW4060 4D panel.cfg:

[fltsim]
alias=CS_B767-300ER-II_PW4060\panel

Seeing as the 767-300ER PW4060 4D model uses the 767-300ER PW4060 model's panel.cfg, you can't make the changes to the 767-300ER PW4060 4D panel.cfg, only the 767-300ER PW4060 model's panel.cfg, and that means the changes work for both models.