I'm not sure I agree with this:
[the technical cookies] are explicitly requested by the user when they indicate that they would like to add the item to the cart.
The only thing they requested was that the item be held in a cart for them. They didn't explicitly request that cookies be used to store information about items in the cart. They most likely don't understand all of the options for how to store data like this, and certainly wouldn't know or expect specifically that cookies be used for this.
In fact, localStorage could be used instead. If it's a single-page app, then even that would be necessary; it could all be kept in page-local variables until they checked out (all on the same page); such that reloading the page would cause the cart data held in those variables to be lost.