Thanks so much for the feedback! You understand the feature perfectly, and, as you have discovered, you also accurately identified a bug. Thank you so much for discovering it; using Polylang sounds like a superb way to test the page naming features.
The description of the settings is indeed how things are supposed to work. All the places the generator needs a page name, it should ask WordPress first. If the name comes back empty, only then should it go to the settings. It looks like I missed this step for the 'root' of the breadcrumb trail (which maybe a static page or the 'home' list of recent posts). Seems there's a case there I missed.
Your solution appears to be the exact answer required for page_on_front - I hope that has temporarily resolved the issue for you, and I will go ahead and do an update on the code to include this fix soon! Thank you so much again, and I would love to hear any further suggestions or feedback.
Chris