[anishmehta24]

?sql-data=false on an instance is parsed into InstanceConnConfig.SQLDataEnabled, but the proxy checked instance is true || --sql-data, so with --sql-data set globally the instance still connected through SQL Data, got a Postgres port and skipped the cache warmup. private-ip and psc already let the instance value win over the flag; SQL Data now does the same.

Since SQL Data only supports Postgres, this is what you'd use to keep a MySQL instance on a normal connection next to Postgres ones:

./cloud-sql-proxy --sql-data proj:region:pg 'proj:region:mysql?sql-data=false'

Added a port selection case to TestClientInitialization and a case to TestSQLDataWarmup; both fail on main. Ran go test ./internal/proxy ./cmd on Linux (WSL).