https://nginx.org/en/docs/http/configuring_https_servers.html#single_http_https_server has the following note:

The use of the ssl directive in modern versions is thus discouraged.

The ssl directive was removed in 1.25.1 and is not present in any of the supported versions. It feels like "discouraged" is not strong enough to reflect that.

The relevant paragraph starts with "Prior to 0.7.14", so I doubt this note has any value except historical nowadays.