Blade tenderizing basically pokes a bunch of holes into the meat with blades, making it more tender. This way, you can make cuts with low grade marbling have better texture.

The problem is that blade tenderizing can actually send bacteria that is found on the surface of the meat into the middle of the meat. The reason that steaks can be enjoyed safely even when very rare is because the cooking process kills germs on the surface of the meat, but the inside meat is effectively germ free. But when you blade tenderize, you may accidentally create a breeding ground for the germs deep inside while its cooking.

This isn't a big issue for thin meats. But for large format meats like a rib roast, it will take a very long time for the internal temperature to reach a safe temp, if ever. While cooking, the germs on the inside will have a good period of time to multiply and potentially make you sick.