Well, he's basically right. For example, you could do this...
<VirtualHost 192.168.1.254:443>
DocumentRoot /var/www/domainname/html
ServerName www.mydomain.com
ServerAlias mydomain.com www.mydomain.co.il www.mydomain.de
SSLEngine on
SSLCertificateFile /etc/httpd/conf/ssl.crt/mydomainname.com.crt
SSLCertificateKeyFile /etc/httpd/conf/ssl.key/mydomainname.com.key
</VirtualHost>
Provided dns for these 3 domains points to 192.168.1.254 (in this example), all domains lead to the same document root. However, When you buy an SSL cert. It only works for one domain, and that's only if you buy a wildcard type. Typically, the certificate is per URL (i.e. www.mydomain.com. Not catalog.mydomain.com, etc.) You can still connect, but you get a certificate mismatch error or a warning that the certificate cannot be verified using one of the many stock certificate authority certificates that come with your browser (ever wonder what the root certificates updates were all about in Windows?)
Keep in mind, I am not an Apache guru. Furthermore, this is NOT an Apache forum. You may find further help on an Apache specific forum.