Yes, that is (mostly) true.
The App uses ipv6 link local addresses (fe80::.. + mac address). But it also tries to make use the received IPv6 network prefixes. Also, the last contact address is stored. These approaches improves the probability a bit to find the contacts in other networks.
As a side note, many mesh networks are emulating a layer 2 network. With this, everybody can build up their own decentralized telephone network.