As of SQL 2011, there is an official ISO SQL standard for temporal tables. See the description here: https://sigmodrecord.org/publications/sigmodRecord/1209/pdfs/07.industry.kulkarni.pdf

Postgres has an open commitfest for implementing system versioning https://commitfest.postgresql.org/34/2316/. However, they are struggling to decide upon the best implementation. Would the contributors/maintainers of this repo maybe be able to reach out on that CF email thread explaining the design decisions for this plugin? That might help them come up with the best way of doing things, even if there is no contribution to the code.

If this plugin is planned for continued development, I'd also suggest giving it a SQL11-compliant syntax. However, it seems development might be stalled, so maybe it's best to go all in in a PG adoption of temporal tables, as in the commitfest.