Hate to say it but more than 50% of those pictures show the work of modern knappers, but that doesn’t take away from the skills and imagination of the Mayan relic’s. Look up Giza Blades and you’ll see another interesting method of knapping. These blades were cut into slabs using copper saws and then hand grinding until the proper radius across the blades were met. They then used a mechanical pressure flaking device similar to one shown in your link.
When you say that half of those pictures were probably modern, did that include the ones that had Aztec or Mayan profiles as part of the design, or only the other fancy ones.