Seems like it's not that major of a blow, just that human creation of such tools requires a higher standard of evidence now, such as "concrete traces of dietary remains or hearths—charcoal at the site could have originated from naturally occurring fires," as the article says. Ultimately, though, the farther we go back, the harder it will be to tell human-made from other primate-made tools, as the other pieces of evidence more readily decompose.