Yes, all production system could be built using two database: One for metadata, one for dynamic data. Or two tables: one for metadata, one for dynamic data. What's strange here ?
strange or completely a-typical for 99% of web apps?
Not sure what web apps you've worked on but the rest of the world doesnt default to anything like this. Even if it does make sense for the usecase, even Reddit only evolved to this much later.
Furthermore, you can have several metadata tables that represent different types of graphs of the data tables, using all the relational features.
For example, one can implement role-based ACL on a tree structure in metadata tables, with one data table. Then sql can be used to get permissions, and even join on the data table, if that works for you.
