I think that statements like this are usually written more for political than for scientific reasons. Yes, "races do not exist" is true in the sense that 19th century classifications made by racist Europeans do not do a good job of mapping the reality of human genetic diversity. However, race does exist in the sense that, for example, two randomly selected people from China are likely to be closer to each other genetically than either is to a randomly selected person from England - and not only that, but it is also likely that the average person or, for that matter, computer algorithm will do a fairly good job of guessing people's genetic distance based on their visual appearance, at least for relatively large genetic distances.

I feel that too often, politically motivated people pick up on such academic statements and use them to justify implying that the very concept of racial difference is inherently empty or wrong and perhaps should even be tabooed. It is a bit of a motte and bailey technique: you first say, "Look at these statements - see, science rejects the very concept of race - any discussion of racial difference is thus unscientific and in any case what are you, some sort of bigot?" And if anyone pushes you more closely on the matter you can just retreat to the actually justifiable position, "Oh well of course I did not mean that there are no identifiable patterns in human genetic diversity, that would be absurd, I just meant that old European racial classifications are inaccurate."