However, it sounded like every employee at SpaceX went home on Friday thinking "Do I still have a job come Monday??". Because no other information seemed to have been imparted as to the selection criteria for the redundancies, every single employee wouldn't have known if they would keep their jobs or not.

Unless they knew they were blatant underperformers or had lots of black marks against them on file, their chances of keeping their jobs was the same as the chance they could be on the 'hit list' for redundancy. 50/50. I am willing to bet that even employees who thought their job was as safe as houses and that they were considered good employees would find them self on the 'let go' list.