You should probably realise that the world has radically changed since then. This kind of thing works when you have a significant lead in the field that makes keeping vulnerabilities open sufficiently low risk for your own side. But if your adversaries have similar capabilities, then the calculation changes.
Has anything changed? Governments are hoarding undisclosed vulnerabilities, using them as they see fit instead of fixing. Every espionage, surveillance, or war campaign (see Russia v Ukraine, US/Israel v Iran etc) is followed by a ton of burned 0-days.
>This kind of thing works when you have a significant lead in the field
No? It works even if the adversary has the same capabilities. It only stops working when everything is fixed.