If it has legitimate titles added later, those should be on all releases with an annotation. It’s not uncommon to see a release with one or a few tracks given a title from a different source. You should never use [untitled] for tracks that have a title, even if there’s no title printed. Again, the guidelines are very clear about this.
If the artist gives the track a name somewhere else (for example, on their website) that name should be used instead of [unknown].
https://musicbrainz.org/doc/Style/Unknown_and_untitled/Special_purpose_track_title
We shouldn’t “respect” metadata provided on Bandcamp etc. Files from there often contain things like album artists in the album/track tag with the label name in artist tag. That’s not intentional either. There’s no checkbox for untitled tracks on Bandcamp that formats them uniformly. There’s no enforced style guidelines at all on Bandcamp, but there are on MBz, and that’s why people often prefer to use MBz metadata to tag their files.