Basically, it is something specific to OSPF3 to ID the links. For example, on the Hello Packets for OSPF(2) we have Router ID and other fields (section A.3.2 of RFC1583), while on OSPF3 the Hello Packet:
The Hello packet now contains no address information at all.
Rather, it now includes an Interface ID that the originating
router has assigned to uniquely identify (among its own
interfaces) its interface to the link. This Interface ID will be
used as the network-LSA's Link State ID if the router becomes the
Designated Router on the link. RFC5340
This would mean that this is expected behavior, as on OSPF2 you have the LSA ID, while on OSPF3 you have the Link ID.
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