The DECT Nr+ shell (the MAC version, not the -phy; tested with v3.3.0-ba167d9f3db4) offers IPv6 connectivity.
The DECT standard has a profile for IPv6 described in ETSI TS 103 874-3, which describes how IPv6 is transported over DECT Nr+.
Observing the same IP exchanges over the API, the IP packets come in unmodified inside the channels, rather than using the CVG layer endpoint 0x8002 or 0x8003, which would appear to indicate that the traffic is using a bespoke version I'd characterize as "IP packets dumped directly onto the MAC layer".
Is the intention of that example to implement ETSI TS 103 874-3? Does the traffic exchanged reflect that intention? If the intention is to deviate from 103 874-3, is there a name that was given to this mechanism of sending IP traffic over the MAC layer?