Link to paper.

Figure 2 shows the basis of their analysis; cumulative ratings showed a small increase for Asian restaurants and were more-or-less flat for others.

Figure 5 shows the differences they report between their modeled synthetic ratings and the actual ratings. There's a clear increase for Asian restaurants (black line), although arguably it's continuing the trend from the prior few months. Three other lines have slight declines (Latin, Italian, Mexican), and two have slight increases (Caribbean, American). The paper says the two with increases can't be counted, but doesn't clearly explain why:
> "We were able to find robust synthetic controls for many cuisines, but were unable to calculate robust controls for Caribbean and American cuisines. Yet for Caribbean and American cuisines, the gap between actual and synthetic does not change before and after December 2019.
> For both American and Caribbean cuisines no conclusions can be drawn regarding their synthetic controls since it assigned a weight of 1 to Italian and Latin cuisines respectively, meaning that their comparison groups are not a weighted average of other cuisines but rather only one cuisine that resembles them the most."

First, I don't see how their model could reasonably assign all of its weight for American to Italian and for Caribbean to Latin. Looking at Figure 1, the monthly citations for American (dark purple) are very different from those for Italian (light purple); in particular, Italian has a huge spike down in the second half of 2021 whereas American is largely flat over that period, making it much more similar in movement to Latin. Similarly, the monthly citations for Caribbean (green) are very different from those for Latin (red); in particular, Caribbean has a massive spike up and down, totally unlike the relatively-flat Latin.

Second, it's simply not the case that the gap for these cuisines does not change before and after December 2019; it's clear from their Figure 5 that both increase, one continuing an increasing trend and the other reversing a (short) declining trend. Perhaps these increases are not statistically significant, but no statistical significance is described or examined anywhere in the paper. Their analysis boils down to "look at these lines".

So while I agree with their general premise that anti-Asian racism definitely spiked after covid, and it seems very plausible that that would drive some of the increase seen in citations of Asian restaurants, without actual statistical analysis there's no way to say whether that's just noise in the data or an actual effect. My guess is that there is statistical significance there, but they haven't done the work to allow anyone to conclude that.