My hope is that they'd hope a candidate would be able to identify the connection to run length encoding within the pattern.
Why do these puzzles emerge at big companies? It looks like a sort of institutional power trip emerges: "if you want to work with us, you need to be real good, and these are the sorts of problems we want you to think we deal with every day!" Except in most cases, they aren't, and there are plenty of mediocre folks already employed there. But the institution NEEDS to believe it only hires the best, and one way to perpetuate that belief is to haze new applicants more and more. All it really produces is candidates who are very lucky, or very compatible with the existing culture.
Hiring is hard, and puzzles are a fail-fast mechanism that is terrible, but produces some sort of results, so it gets used.