I doubt this makes you feel any better, but I know of many people laid off between December and February who still only received 50% of their bonus, and I know of people laid off in those time frames who didn't receive any of it. After all, the more they pay out a laid off employee, the less they can give the survivors. Each leader gets a bucket to work with. I have even personally witnessed senior leadership intentionally reducing bonuses for existing employeees to spread the remaining wealth amongst themselves, before they even got to rifd employees.
An August layoff with a September termination date does virtually guarantee no bonus, but being laid off even in Q4 or Q1 wouldn't protect you. When there's a way to sc--w over the employee, they find a way.