When I was last looking -
Studio apartments and one bed room apartments rented for similar amounts, and so did two beds and three beds.
But the price jump from one bed to two bed was much larger than any of the other jumps.
You can speculate on many reasons why this might be the case (smallest size apartment for a family in the city, smallest size you can split with a friend, smallest size with space for an office).
There are exceptions and I'm sure that more research time could help you find them.
But one of the points made convincingly in the artle is that if you are poor you don't have a lot of energy, time or gas-money to do that kind of research.