I agree, comparing to other expensive markets seems a bit odd, rather than comparing to markets with some other similarity (population, geography, median income, et cetera). The full table in the original report is much more interesting:

https://www.zumper.com/rent-research/national-rent-report

Many interesting comparisons to be made, especially places where rents fell YoY despite population growth.

It's actually a combination of both, leaving out more expensive smaller markets.