Sexual preferences are discriminatory in principle, just for starters they are inherently sexist for the overwhelming majority of the population, most people are attracted to only one gender, not to mention, attraction is clearly agist, also height-ist, and honestly all the "ists" you can think of. We discriminate, in the literal sense of the word, when looking for a sexual partner. We are not attracted to everyone equally.
How much it reflects the racism of your society is up to debate, and I don't think you can discard it completely but neither you can argue that racism is the only reason people are more attracted to a race over another. And it is certainly beyond anyone's control, you like what you like.
I've come to discover race is a weird and arbitrary thing anyway. I'm a colombian living in Brazil, strictly I am descendant from spaniards and indigenous people, so I am literally mixed-race. However in the US I would be hispanic/latino, people say that is more an ethnicity but even the article in the OP treat it as race. Back home I'm darker than most of my family, which is why my parents nicknamed me "negro", this is actually very common. The most baffling and bizarre thing however I found here in Brazil, here I am "white", a friend called me white once precisely when we were discussing attraction and when filing a police report I was identified as white in the document!
I mention this anecdotal evidence because my friends have all a clear preference for "race", however the people they have been with might be classified completely different in the US or even in Colombia. One friend, who would definitely be considered black everywhere, has told me he does not like black people, and I mostly have seen him with people with "white" features, blue eyes, white skin, that kind of thing. However other friend, who I guess would be considered mixed-race, has also said he does not like black people but he was crazy for this guy who most definitely would be considered black in the US and here, but actually in Colombia not that much. Another mixed-race friend really likes black guys, almost exclusively.
Just by looking at statistics 30% of marriages here in Brazil are mixed race while the US is like 1% or something like that. However Brazil can actually be a pretty racist country. I have the hunch the results of this study are more about segregation than racism, both can go hand in hand, but not necessarily, and your upbringing most definitely affects your preferences.