not sugaring is probably also an implicit part of the OP’s question…you got a preferred excuse for that slab?
some folks have suggested that too long in the oven, or too hot in the oven can cause this. others swear that material scraped onto the parchment is far more likely to nucleate than material poured out. I’ve seen evidence that the latter is true, and treat the pour separately if I care about the final consistency.
I have also seen relative humidity blamed for the problem. I definitely saw less butter/sugar once I was able to move my operation inside/out of the rain. I also watched a CO import struggle with nucleation when they hit Eugene. Something they rarely saw in Denver. At that point “inside” was not much different from outside once the doors were up and the fans were on. Things got better in July, which is when it stops raining around here. So I qualify as a believer on that one too.
pretty sure most of this is covered in Oven tek SOP criticisms welcome referenced above.