The writing is almost always on the wall for those who get let go - not always, but many times it is if you pay attention. Your normally heavy workload suddenly starts to dwindle while your coworkers are having more work dumped on them. You slowly stop getting invited to meetings, you slowly start losing access to places you normally had access to, your manager/director doesn't have a lot to say in 1x1's anymore, you begin to feel as if you are an "outcast." Maybe that lucrative account you've been on for the last year(s) was yanked away and you get put on smaller accounts that dont make as much money.
It's because they already know, or at the very least know you are a possibility of being laid off. There is no way that managers/directors DON'T know who is getting let go at least 2 months in advance, IMPO. I call BULLSHT that they only find out day of or a week before.
Logically it makes no sense to NOT inform a director/manager that one of your directs is being laid off because if they have no idea then what if they assign you a job/project that is important and in a time crunch, then they get 50% finished, then laid off? That person has no obligation to share anything that they did with their former teammates. They have no obligation to divulge any information on how to finish it, how to fix issues that may be happening, etc... Essentially, much of that project would have to be started from scratch.
If a person who is amazing at their job is to be let go and manager has no idea then, that puts them in a massive pickle as they now need to spend a month interviewing new people, hiring someone, then training, then getting them up to speed on a billion things.
The layoff "lists" are made months in advance as it has to go through HR, then legal, then eventually to admins who begin yanking privileges away, badge access to certain areas, etc...