This is actually a common meme:
https://www.reddit.com/r/ProgrammerHumor/comments/fbwnd0/im_...
https://www.reddit.com/r/ProgrammerHumor/comments/ajthjb/thi...
https://www.quora.com/What-do-people-think-good-programmers-...
How developers dress really depends on the company and the culture there. E.g. in Germany in many of the conservative older companies, wearing a suite is mandatory, and esp also in all those consulting companies. Also in many of the privatized companies like Deutsche Post, Deutsche Bahn, etc. But then, in other more modern software companies, people would make fun of that.
The idea that you must adhere to some clothing dress code rules is really against the open-minded principles of software developers.