Why does safe browsing remove some URLs? Then some of them re-added later on

[lkc0626]

Why does safe browsing remove some URLs? Then some of them were re-added later on.
Other than false positive URLs, why does safe browsing remove URLs? from looking at the local synced database, quite a lot of URLs are getting removed daily. Then some of them get re-added in the future.
Other than false positives, why does safe browsing remove URLs? is it to reduce local database small?