pg_tables is a view, which only loads data from a few other internal tables, but you can modify many of them, yes. (And many extensions do that). Specifically,

pg_tables is a view, which only loads data from a few other internal tables, but you can modify many of them, yes. (And many extensions do that). Specifically, pg_tables is defined as CREATE VIEW pg_tables AS SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.relhastriggers AS hastriggers, c.relrowsecurity AS rowsecurity FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 'p'::"char"]));