TLS 1.3 changed the handshake, and the cipher list you copied

1.3 was finalised in August, and its cipher suites are configured separately from 1.2’s — so a hardened ssl_ciphers line copied from a 2016 guide silently governs only the old protocol.

ssl_protocols TLSv1.2 TLSv1.3;

# 1.2 and earlier
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:...;
ssl_prefer_server_ciphers off;   # 1.3 makes this counterproductive

# 1.3 suites are fixed by the protocol and configured, if at all, via
# ssl_conf_command Ciphersuites — which needs a newer OpenSSL

Turning off server cipher preference is the change most guides had not caught up with: clients generally know better than the server which suite is fastest on their hardware, and 1.3’s suite list is short enough that there is nothing dangerous to prefer against. The other practical gain is the shorter handshake — one round trip instead of two — which is worth more on a mobile connection than most optimisations anyone will do this year.