And the job I want let me wear whatever if feel like. Which excludes polo.
The point of that part of the article wasn't that one must wear a polo, but rather one must look professional if one desires to be treated as a professional.
Wearing nice jeans and a nice button-down can be very professional looking. -- wearing torn jeans and a hoodie into a meeting... not so much.
Even if it's just on those all-day-meetings days where you interface with your PM and other biz types...
"Don't dress for the job you have, but rather the job you want".