Configuring a special-nexthop route like so:

{"special-next-hop": "blackhole", "destination-prefix": "12::0/64", "id": 1, "description": "blackhole ipv6"}

is shown in HC operational data as:

{'destination-prefix': '12:0:0:0:0:0:0:0/64', 'table-lookup-params': {'secondary-vrf': 0}, 'vpp-ipv6-route-state': {}}

but should be:

{'destination-prefix': '12:0:0:0:0:0:0:0/64', "special-next-hop": "blackhole", 'vpp-ipv6-route-state': {}}

Note the route is configured correctly according to VAT and traffic tests, so this is likely just incorrect parsing of VPP API output.