Companies are free to direct list without underwriters and even issue new shares in the process.

I'm not sure what a "pop" (the idea that prices often go up on listing) has to do with anything. It generally means that the company underpriced its equity but by no means does this always happen.

Are you referring to a greenshoe? There's some misinformation there too, but it serves a purpose, too. [1]

[1] https://www.investopedia.com/articles/optioninvestor/08/gree...