PgBouncer introduces its own problems and strictly speaking adds additional complexity to your infrastructure. It needs to be monitored and scaled separately, not to mention the different modes of session/transaction/statement connection pooling. Adding another proxy in the middle also increases latency.

Yes, currently, putting PgBouncer in the middle helps handle massive sudden influxes of potentially short lived connections. That is indeed the correct current best practice. But I hardly fault the author for wishing that postmaster could be configured to run on multiple cores so that the additional complexity of running PgBouncer for this relatively simple use-case could be eliminated.