this is true, they are not the same at all. i mean all the colors you mentioned probably begin their code with the letter "L" but thats where the similarities end. i had to spray cards out for the lambo, audi, and porsche greys mentioned for a customer a few months ago, and i also sprayed some of 1quik240's color in the past on some of his parts. they are all substantially different from each other. i think what he means by them being the same is that by MY understanding VAG's paint is supplied by the maker Glasurit. obviously it can be mixed in any paint line though, if you know the code.
for fun here is the audi nimbus grey and the porsche Graushwarz side by side
the audi (left) has some nifty greenish pearl that adds a little life to it, while the porsche (right) code has nothing like that. its dark and pretty plain but cool for that reason on the right car.
maybe this info will come in handy to someone i dunno haha