Male and Female Orcs

[Nerwen]

The argument I have for Bolg son of Azog is that they were goblins. I think that goblins have a different origin than orcs, and they might breed differently.

No evidence for that, as far as I'm aware, but anyway "Bolg son of Azog" appears in a completed text published in Tolkien's lifetime– as "canonical" as it gets. (Meanwhile, "Azog the father of Bolg" shows up in the LoTR appendices.)

This, if not simply a hoax, as for all we know it may be, is merely one of Tolkien's numerous abortive retcons. He was given to sketching out radical changes to be made to his Legendarium, then abandoning them after a paragraph or two– often, no doubt, because it became clear they were unworkable. The many contradictory versions of the origin and nature of Orcs are a case in point.

Because of all this the "last known version is always the 'true' one" approach is very problematic indeed when applied to Tolkien's writing. The man was quite capable of suddenly jotting down on the back of an envelope:

Originally Posted by J.R.R.Tolkien, in an as yet unpublished manuscript

Elven 'horses' in truth more nearly resembled unicorns. This was of course well known to Aragorn, who showed no surprise at Asfaloth's horn. Frodo's failure to remark on it is harder to explain, but may be attributed to his limited power of observation..."