This study is legitimate. I read through the article and it is definitely trustworthy as it is published in distinguished journals and peer reviewed. As I was researching the topic, I saw that many sources online cited this specific study, but I didn't see very many other sources that corroborated the same claim. So, I wanted to see what else existed in the study of cat behavior and psychology. I found quite a few articles that do.
One of them I found was this study from 2022 that showed that cats can learn other cats' names.
Takagi, S., Saito, A., Arahori, M. et al. Cats learn the names of their friend cats in their daily lives. Sci Rep 12, 6155 (2022). https://doi.org/10.1038/s41598-022-10261-5