Best guess would be that factorization aims to add back the old rough bedrock(where there were blocks scattered randomly up 3 layers above the smooth bedrock layer). This is based on that the config refers to this bedrock as:I don't know, but it has had bedrock for several versions. I had to get rid of some in a 1.6.4 world because laser drills don't work with it, so it's been around at least that long.
I:fracturedBedrockBlockId=2173
But not sure why it doesn't spawn in packs like TPPI though. Something else must be overwriting it.