It wasn't my point. As far as I read it, Capt Blogs was saying the system should be better than 0.3 nm rnp. I am just saying that for all the GNS approaches I have done, 0.3 nm was quite sufficient because of the offset and high missed approach point.
I note on page 2 of this thread, that the GNS approach at VNKT is actually straight in for the last 3 nm, with a decision of just over 300 ft. That is a max 15º lateral turn to achieve the threshold, if you are at the margins of the 0.3 nm error for some reason. Not too bad. I'm sure someone has worked out that that is a sufficient margin. But do bear in mind that the rnp is only a 95% probablity, so five times in every hundred approaches you could be off by more than that.