Wizardry 8 does not think that I killed all of the Rattkin Breaders
Solution 1:
In the end, I visited this page, downloaded this editor, loaded an old save file and and gave myself the Rattkin key and battled again.
This time, killing both of them worked.
Was it a bug? I don't know. But I do know that SirTech folded long, long ago & are unlikely to give support :-(