Project-level custom properties unable to store locally

As per Ready API documentation -  Only test case, test suite, and project-level custom properties can be stored locally.

 Link to url- https://support.smartbear.com/readyapi/docs/testing/properties/local-properties.html

 

I have few properties under project level but the check box is disabled to store locally or I am unable to check check box to store it locally. [Added screnshot]

But I am able to do test case level.

Is this a bug?