Is there value in looking at book, film and song titles for possible inclusion in the sentence examples?
As title aren’t copyrightable (as per here and other official sources online: https://www.copyrightservice.co.uk/copyright/p18_copyright_names) there seems to be no barrier to using them.
As to whether they’d be useful, they could have two area of value
- Titles come up quite often in speech (eg “Play [song title] please”)
- The titles could often include useful words, improving general coverage.
Some cases won’t be as useful as regular phrases, since titles typically don’t form a full or detailed sentence, but they’d provide variety, would be less likely to have grammatical errors (unlike some of the free form sentences submitted by non-native speakers to common voice) and best of all they would be easy to say - no author wants a title that people can’t get right!
On a practical level, lists are readily available online (eg on Wikipedia or in online databases), saving transcription errors. They’d just need someone to go over, sense check them and cut the more obscure ones (eg with very rare names or made up words) before submitting.