> The issue is there's no database feature spec

ISO/IEC 9075 disagrees.

Yeah, that's the query language used in relational databases but find my the spec for "database encryption" or "database clustering"

The SQL spec is barely comprehensive of the SQL dialects found “in the wild”, let alone the entirely independent and much more interesting set of non-table managing/querying features databases provide.

It provides at best a baseline for comparison.. and a fairly shallow one at that