Matzah sold as Shmurah means that Jews were present from the time of harvesting, making sure that the grain stayed dry and didn't become chametz, and intending for the purpose of the mitzva of matzah.
"Regular" machine matza, if I understand correctly, is only "guarded" starting at the time of kneading. But I assume they'd only use flour they have 99% (99.999%?) certainty has not come into contact with water. How/where do they find such flour?