Look, entire industries exist for being complaint with the letter but not the spirit of the law so I'm sure that this in no way meets the definition of a cookie as far as the GPDR is concerned.
However, this is absolutely a cookie. Scraping just enough information from the browser to create a unique but stable hash and then having the browser compute it every request isn't at all different from that browser information acting as the cookie.
Technically no - cookies are stored by the user. If anything it is technically worse in some ways because it moves it to the back end outside of user control.
However, this is absolutely a cookie. Scraping just enough information from the browser to create a unique but stable hash and then having the browser compute it every request isn't at all different from that browser information acting as the cookie.