Is this true? My best guess is that sentences past #328231 are added by contributors of Tatoeba Project. That is, up to that point, the majority of sentences are marked "date unknown" in the "Logs" section. What's the real story?

(Maybe the ID of this sentence got changed by an error in the deduplication script? :)

It's not true... anymore.

The real story is that this sentence was added a long time ago, in a previous version of Tatoeba. In that previous version, the corpus was not structured the same way as today. There was only one table and sentences were linked to each other via their id. A sentence and its translations had the same id. Basically, the pack of sentences you see up here would have had the same id.

Today each sentence has its own id, and there is a separate table to link sentences to each other. So obviously this sentences is not true anymore :)

It used to be true though, and this sentence was used as a reminder to separate sentences that were from the Tanaka Corpus and sentences that were from Tatoeba itself (because a long time ago, Tatoeba was not the place where the Tanaka corpus was officially maintained, WWWJDIC was the official place).