This reinforces doubts about contact as strategy for promoting equality.

Hmm.  From Does intergroup contact foster solidarity with the disadvantaged? A longitudinal analysis across seven years by Nikhil Kumar Sengupta, Nils Karl Reimer, Chris G Sibley, and Fiona Barlow.  From the Abstract.

Contact theory is a well-established paradigm for improving intergroup relations – positive contact between groups promotes social harmony by increasing intergroup warmth. A longstanding critique of this paradigm is that contact does not necessarily promote social equality. Recent research has blunted this critique by showing that contact correlates positively with political solidarity expressed by dominant groups towards subordinate groups, thus furthering the goal of equality. However, this research precludes causal inferences because it conflates within-person change (people with higher contact subsequently expressing higher solidarity) and between-person stability (people with chronically high contact simultaneously expressing chronically high solidarity, and vice versa). We addressed this problem in a highly powered, seven-wave study using two different measures of contact and three different measures of political solidarity (N = 22,646). Results showed no within-person change over a one-year period (inconsistent with a causal effect), but significant between-person stability (consistent with third-variable explanations). This reinforces doubts about contact as strategy for promoting equality.

The study is conducted in New Zealand.  

I have always been substantially dubious of this form of study because, in the US, it is so often cast in terms of race whereas I think the true variables of importance are class, culture, behaviors and objectives.  Regardless of race, if you spend time with unknown people who have similar class, culture, behaviors and objectives, then you will get to know them better and support them.

Conversely, if you end up spending time with people of different class, culture, behaviors and objectives, the chances of sympathetic bonding are more complicated and challenging.

For years I have worked with many and large teams across national and continental boundaries.  Many of these teams are extremely heterodox in terms of race and national origin.  However, they are virtually all upper middle class with shared advanced educational attainment and comparable life ambitions.  It is rare to encounter anything more than the ordinary level of team conflict, frequently centered on miscommunication.

I also work with teams within countries where race is not an issue but class/religion can be.  It is not uncommon to encounter significant challenge.  It does get worked out in the end but the differences in what is considered appropriate behavior or goals can be striking.  

The obsession with boiling all inter-personal conflict down to presumed but undocumented racial bigotry is both empirically bankrupt and bigoted in its own right.  I am disgusted and revolted by the ignorance and the prejudice.

This particular study is entirely consistent with my perspective.  

Simply mixing people of different conditions together serves no purpose.  If they have important things in common, the mixing serves as a catalyst for bond formation.  If they don't have anything important in common, the bonds do not form.  

And independent of that dynamic, if there are pre-existing tropes, biases or stereotypes, positive or negative, then the mixing is mixed depending on whether the tropes, biases or stereotypes are consistent with the behaviors seen in the context of the team.  

For sixty years we have been focusing on the diminutively salient issue of race and have not focused on the more important issue of how to build bonds across barriers (of whatever sort).  Simply mixing people together and hoping for the best was a conviction for which there has been little supporting evidence.