This rumour doesn`t even know math for what it seems.
Sony original production plan was 5M, then they doubled it to 10M. So when they revise it down by 4M it ends up at 11M? That is pretty funny.
The way I understood it was that in July they were expecting to have 10M manufactured by end of 2020, the 15M was supposed to be the amount shipped by end of fiscal year (March 2021).