4AGE Big port head failure

[The Doctor]

The cam seal leaking would tell me that it did get oil delivered?
There's oil spraying around in the head. The seals are there to keep it in the head area before it makes it's way down to the sump
My guess is that it went wrong from the first start after the rebuild and slowly ate away the bearing surface. Maybe some oil galleries are blocked? After that the shrapnel did the rest.

Or did it leak so much you basically ran the sump dry? The oil light won't come on until there's less then 0.2 bars of oil pressure, which is basically dead engine territory anyway.