psql sslmode behavior and trace_connection_negotiation in PG17

Hi

I tried to connect with psql + client sslmode = require + server requiring
ssl with PG17 and trace_connection_negotiation = "on". So "SSLRequest
accepted" is logged twice with two different PID. I believe the PID 15553
is psql and 15554 is the PG backend. How do you explain the two connections
with SSLRequest? From the log, it seems psql made a connection to itself
with SSLRequest and proxied that to Postgres server with a full SSL
negotiation. I never saw a log on 15553's connection being closed when I
closed the psql process. Does this behavior match what was talked about in
the below hacker thread on additional connection?

2024-07-17 03:06:54.492 PDT [15553] LOG: connection received:
host=127.0.0.1 port=54002
2024-07-17 03:06:54.492 PDT [15553] LOG: SSLRequest accepted
2024-07-17 03:06:59.982 PDT [15554] LOG: connection received:
host=127.0.0.1 port=54004
2024-07-17 03:06:59.982 PDT [15554] LOG: SSLRequest accepted
2024-07-17 03:06:59.994 PDT [15554] LOG: connection authenticated:
identity="postgres" method=md5 (/usr/local/pgsql/data/pg_hba.conf:18)
2024-07-17 03:06:59.994 PDT [15554] LOG: connection authorized:
user=postgres database=postgres application_name=psql SSL enabled
(protocol=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384, bits=256)

https://www.postgresql.org/message-id/flat/CAM-w4HOEAzxyY01ZKOj-iq=M4-VDk=vzQgUsuqiTFjFDZaebdg(at)mail(dot)gmail(dot)com