One of the companies I interviewed at had me do this exercise at the end of the interview and to be frank, I bombed it quite badly. One issue was the syntax was so weird compared to the type of code I'm used to writing and reading from others in library code that it was hard for me to comprehend the logic without the benefit of looking it up.

I was filled with anxiety working under the time pressure to understand a document of code which I had very little context of, and no previous relationship with the reviewer so I kept thinking to myself whether or not the question that came into my mind was stupid obvious.

In contrast, when I had take-home tests, I scored exceptionally high on all of them, leading to offers. I recognize that a lot of people here hate them because of the time involved and it's akin to spec work, but IMO it felt much more like my usual day-to-day life as a developer.

One of the take home tests had existing code to work from but again, working at my own pace and having access to online resources to read docs was much less anxiety provoking.