statio_user_tables shows only postgres database schemas

What did you do?
installed and configured postgres_exporter. aside postgres database, there is another one, let's call it userdb
What did you expect to see?
metrics like pg_statio_user_tables_tidx_blocks_read for tables in database userdb
What did you see instead? Under which circumstances?
I see only metrics for schemas in postgres database. looks like it doesn't have access by default there? to see pg_stat_user_tables for schemas in userdb I need to connect to it first, but you say in readme that connection string should consist of only postgres database

Environment

• System information:
  Linux 3.10.0-1160.6.1.el7.x86_64 x86_64

• postgres_exporter version:
  postgres_exporter, version 0.15.0 (branch: HEAD, revision: 68c176b8833b7580bf847cecf60f8e0ad5923f9a)
  build user: root@88f74f2c2888
  build date: 20231027-14:38:56
  go version: go1.21.3
  platform: linux/amd64
  tags: unknown

• postgres_exporter flags:
  PG_EXPORTER_DISABLE_SETTINGS_METRICS=false
  DATA_SOURCE_URI=:7430/postgres?sslmode=disable&host=/tmp
  DATA_SOURCE_USER=postgres
  --web.listen-address=0.0.0.0:9187 --collector.stat_statements --collector.statio_user_indexes
  --collector.long_running_transactions --collector.database_wraparound
  --collector.stat_activity_autovacuum --log.level=debug

• PostgreSQL version:
  postgresql 11

• Logs:
  no errors
  collector.go:206 level=debug msg="collector succeeded" name=statio_user_tables duration_seconds=4.023973512

Start with collector.go and the statio_user_tables collector, then review the README connection-string guidance. Reproduce the behavior on PostgreSQL 11 with the postgres and userdb databases; done means metrics for userdb are exposed or the supported limitation is documented.