So let's assume the rumors are true that Aug 5th will be the EOI submittal date and Sept 12 is the official layoff date. What happens during that 5-week period where your boss and boss' boss already know that you're gone, but you're supposed to continue working as if you give a f---?
Then other people start to find out that you volunteered. In meetings, people may start making awkward comments towards you. Others won't be able to rely on you for anything because you no longer care about your future within the company. I just imagine a very tough and awkward time period there.