Upvote:3
As your experience also confirms, the travel waivers do allow you to rebook United iteneraries that include flights operated by partners without a change fee.
I went through a similar experience. My niece was returning to Europe from Houston the day Harvey was supposed to hit. She was traveling on United with a connecting flight on Lufthansa.
I called United before they posted the travel waiver and was told that United would be happy to waive the change fees for the United flight but they could not do that for the connecting Lufthansa flight. I declined to rebook at the time.
I called again later that day after the travel waiver was posted and was then able to rebook both flights with no change fee.