"National Labor Relations Board is requiring Google to post a list of employee rights at its headquarters".

Requiring Google to post a list at hq doesn't cover other locations and/or browser notification when visiting certain sites.

I know but I was trying to answer your question

> did she add a company policy or guideline by adding what she added? I wouldn't classify a union drive as a company policy.

The answer is that it's a policy that must be posted (just not necesarily there). It wasn't a union drive.