The Advanced docs mention extras, specifically "support for mssql". Should this say 'as a backend' like all the others on that list? Otherwise I'm not clear what that optional component does. https://docs.meltano.com/guide/advanced-topics#installing-optional-components

It's rather used as the system db, which yes functions as the default state backend. I'm also noticing that the system db docs don't mention that it's used as the default state backend. Would you mind creating an issue to fix the docs?