That does not help because following that example I should use:

server {
listen 443 ssl;
server_name www.sub1.example.com;
ssl_certificate www.sub1.example.com.crt;
...
}

server {
listen 443 ssl;
server_name www.example.org;
ssl_certificate www.example.org.crt;
...
}

But the first server declaration does not apply the different certificate, instead it applies the certificate of the TLD, so I guess either I can't declare a server with server_name equal to a subdomain of an already declared TLD.