> Best to use a database with native bi-temporal support, a query planner can get very confused about tables with bi-temporal columns and few constraints

Why would they have few constraints, unless the DB lacks adequate support for the kind of constraints that logically apply with temporal data (now, admittedly, many databases do lack that support, but Postgres via exclusion constraints on ranges doesn't, and the functionality, while supporting bi-(or tri- or quad-, or N-, which once you start analyzing the temporal relations that logically apply to data are much more common than one might think, there's no magic universal model)temporal data, isn't limited to just that.