No, it says it will apply an appropriate refund and is an EXCEPTION to the IDB rule and does NOT fall under it. The words you quote "no extra charge" is part of a sentence that says UA will not charge you.

The commitment doesn't define downgrade nor denied boarding. That is the "headline". The terms are defined in the rather extensive document called the CoC. The commitment doesn't state how, or what, it only gives a rough idea, and one should read the full text that explains the details of it. Most headlines on a newspaper have detailed text under them. For the full text and accurate information, one needs to read the whole text, where terms used loosely by some are specifically defined. To believe that UA' rules are summed up in 10 or so 1 sentence lines is absurd. The spirit of UA's policies to it's customers may be there, but the devil is in the details, and it take pages and pages to spell those details out.