I don't know about your case, but in general it may be possible that some "random HR guy" restricts the managers from personally informing their employees, maybe to ensure that all employees are given the same information (and not given information HR doesn't want to reveal). Maybe it's to prevent one manager from letting his/her subordinates spread the word.
I manage people now. I don't care if the general counsel of my company restricts me, if I have to lay off half my team (or even one person) that worked with/for me for years, I would find a way of explaining the situation, taking blame (where due), and making sure they know I would do everything I can to help them find another job.
In my case, the only contact all of us had with the manager was an email the previous night, asking us to come see him in his office. When we reached his office, he was no where to be found, instead an HR person directed us to a conference room and finished the formalities. The only time I saw the manager is when he scuttled past the conference room to his office and stayed locked in there till we left.
