That is true. Anonymity in the Internet does not exist without strong encryption. Therefore, the data traffic is encrypted several times, namely from JonDo to every single server within a cascade. That is the reason why neither your provider nor eavesdroppers in the WLAN are able to find out which web sites you are visiting.

Additionally, the encrypted data traffic contains a special padding which prevents an observer to guess the visited web sites out of patterns in your data traffic. This is a difference to VPN-Systems where such an attack is quite possible.