Today, nearly one month later, following got realized: browsing history of Safari currently in use (few weeks past Catalina migration) includes deep/long timeline which reaches back to late 2021. Finding was made on start of history.db analysis in course of preparation to manual migration of two histories: the one prior to migration and the another past migration. Safari history menu as of this minute is blank (this happens quite often) however history manager presents deep history timeline pretty well. Remembering those few days immediately after migration when Safari presented browsing history only for one, two last days. I was not ready to overwrite short history formed first two days past migration with the former one (the long one), as lot of research was conducted in web those 2 days. Certain maintenance process must been running in background afterwards.