That is true and you should be wary of comments from people on the internet. However, where I live I have never heard of this preparation with this mushroom. There are some species where it is recommended (Armillaria spp. - I did it the first time when I tried them to see if my stomach can handle them. I could but they taste like nothing afterwards. Now I just cook/fry them for 20 minutes and it's fine. Amanita muscaria is another example which needs quite a bit of preparation if you want to eat it for culinary purposes. Haven't tried them yet though.) but with Lepista nuda it's the first time I heard of it. And I don't know anybody who precooks them before eating.

There are a lot of differences regarding edibility of mushrooms in different parts of the world. In the US they eat some mushrooms which are considered inedible here. Eastern european countries eat pretty much anything from what I've read. ;-)

If it is recommended in your part of the world, maybe it's better to stick to the advice. But I'd be interested in the source if it's online and can be translated by google. ;-)

Better safe than sorry is good advice when it comes to mushrooms. :-)