There has never been any guarantee or marketing from AMD's side that any of the locked cores would unlock and work. If the cores were fine why lock them and sell the CPU cheaper?
I would suspect the following:
If AMD finds a certain percentage of its CPUs are not up to the task of a quad core, they would just turn the entire batch into dual/triples. This means that some of the dual/triples are fine and unlocking them can be done at no loss.
But AMD doesn't guarantee it nor do the mobo vendors. They also will probably void a warranty on any component that has been damaged due to unlocking the cores much like they void a warranty on a CPU fried from overclocking.