The story just as many of the other Old Testament stories though particularly those in Genesis is told according to traditional versions rather then as the stories really appear. That is the stories have been adjusted to make them flow better and of course to fill the needs of those telling the stories. EGW did not originate the error that Noah preached for 120 years that error was well established long before she wrote about it. Of course the 120 years has no contextual bearing on the Noah story. Of course the Noah story said nothing about Noah preaching to anyone that idea came from the New Testament where Peter said Noah was a preacher of righteousness. Though as most commentaries will probably point out that can either mean that he lived a righteous life or that he preached righteousness. For whatever reason people seemed to like the idea of Noah preaching a coming flood and people laughing at him it made the story more interesting no doubt. It filled the need of some telling the story and it became a tradition. Truth however has to question traditions.