If you mean the genuine Bundeswehr / German Army surplus then its made from Sympatex, not Gore-Tex. Similar but not the same. Very good quality. I’ve worn this jacket in wet weather for years, on my second one now. I’ve also got a genuine British Army DPM rain jacket which is also good, a size larger to wear over a parka inner in winter.
Yes I guess they are slightly noisy. Not that I really notice it. I don’t do that much in the way of really close in stalking, if I do then it’ll be quite a wet windy day with the wind in my face. The noise of the weather usually overrides the noise I make, can’t think of a time I’ve spooked animals because of noisy clothing. The noise of chambering a round is way noisier than gently pushing through vegetation in my rain jacket. One thing to consider is that the Sympatex doesn’t catch on thorns and snags anywhere near as much as softer more expensive fabrics and this is a big deal for me.
I think the question is valid obviously, but the type of vegetation on the day, the weather, and the individual’s tolerance of noise and definition of “noisy” will make it hard for you to get an objective answer.
I treat my rain jacket, parka, trousers and shirts - all genuine Bundeswehr - with NikWax. The rain jacket is totally waterproof and I only put it on in proper rain. The other layers are shower proofed and water resistant. It’s very durable gear. And invisible to deer!