The new style AIS briefing system was introduced 22 August 2002
Here we go again
Almost nobody (outside those who spend their lives on these internet forums) had heard of it back then.
It didn't work properly even by summer 2003. I busted a Frog nuclear power station TRA then, and narrowly escaped having the CAA prosecute me on behalf of the DGAC. I was able to show that a) the info didn't appear in the narrow route briefing and b) I was receiving a Frog radar service
at the time and they obviously chose to not tell me (but they did so kindly remember to ask me my full details including my inside leg measurement, so they could fill in the forms). The Frogs were arrogant enough to supply a radar track printout showing the squawk they allocated to me
It works well today, but it's much too late for many pilots, and it will always be too late for the big majority of active PPLs, who fly outside the training system, often flying simple aircraft from nameless farm strips, have better things to do than read the drivel on PPRuNe, drivel on flyer.co.uk, drivel in other pilot forums, and who will probably not discover this for another 10 years.
Got to remember that nearly all those who get a PPL today drop out nearly right away, so even if ab initio training was "fixed" overnight, only a small trickle of people knowing this terrible Masonic secret will find their way into the active PPL community.