I haven't read the original story in Gazzetta dello Sport, but this one is explaining what Gazzetta wrote:
https://www.road2sport.com/2016/01/23/f ... formula-1/
According to this article the reason for this additional chicane is so that LMP1 and SuperBikes can go straight at the first chicane, which is a bit too tight for them now. Currently if you send them straight through the first chicane, they are too fast at Curva Grande to be safe.
The current layout of Curva Grande will not disappear, this chicane will just be the 'alternative route' for some classes. So basically F1 would have the choice to use the new layout, without first chicane, or the old one.