(That said, it looks like both PostgreSQL and MariaDB include additional
columns beyond those mandated by the standard - you can't rely on those,
of course. And some databases like Oracle don't even have an information
schema.)
Given the documented charter of information_schema I'd present your conclusion and evidence to pgsql-bugs...while I suppose extra columns are not inherently harmful at minimum they would need to be documented if kept.
David J.
