That's partially true. However if you force TCP connections (in Toxic this is done with the -t flag) your IP is effectively hidden from your contacts because all your traffic gets relayed by TCP nodes in the network. The downside is that forced TCP connections are slower and less reliable.

Though to be properly anonymous you would need to run it through Tor: https://wiki.tox.im/Tox_over_Tor_(ToT)

The reason Tox doesn't have built in anonymity is because strong anonymity has a massive impact on quality (especially streaming data like audio/video). Our goal is to steal normal (non-paranoid) users from Skype and get everyone and their mother using strong encryption. In order to achieve that we need to have comparable quality rather than something that feels like you're using a 28.8k modem.

And again, anyone who actually wants anonymity still has that option.