In reading through the function, I do not see anything that inherently transforms it. I’m relatively certain that there are no transforms (except maybe autop) until the display of the data. I would recommend trying one or two posts, making sure that it’s going to insert correctly, and then going all out.
Also, depending on how things are structured, you may run into a pretty severe issue with Apperance->Menus if you use that many posts, just as a heads up.