I'm as confused as the next man, but I believe ICAO NADP 1 is 800/3000. The older ("former" in ICAO's words) is NADP A which was/is 1500/3000.
You are correct indeed. The only change that took place between ICAO A and NADP1 is that the minimum alt. at which thrust reduction is possible under NADP1 is 800' vs. 1500' per ICAO A.
However, the reason 1500'/3000' are the most common NADP1 figures today, is because airports like EDDF do not want thrust reduction below 1500'. This 1500' minimum thrust reduction height was and continues to be a requirement/recommendation to best satisfy the noise requirements without receiving a big $$$ bill exceeding the noise limit.
This is probably why some of the original posters colleagues have informed him you cannot reduce to climb thrust below 1500' in Europe.
Can you at some airports? Of course, but should you at others? Not if you want to play it safe with the noise violations. And as long as it is safe, there is no reason not to.
Of course some will continue to use 800' and depending on the aircraft they operate may indeed never trigger a noise monitoring point. Ultimately, if the airport wants you to use 1500' for thrust reduction under normal circumstances, and it is safe to do so, there should be no reason not to. And hence most operators have adopted 1500'/3000' for NADP1. Unless conditions warrant different figures.