Absolutely. The article glosses over the other security features that are required to create a card number that would pass the extensive authorization process in the card networks. The information in the article is already in the public domain, so the 'exposure' doesn't increase fraud risk to anyone other than the companies offering 'free trials' for merely providing a number that passes a checksum test.

The amount of security in a particular system is typically proportional to the value of what is being secured. If the companies using a mere checksum test thought the process needed to be more secure they could do a real authorization against the number.