If your computer is locked up, you have to use ctrl-alt-del, with its menu of options including the task manager, in order to interrupt the current processes locking up the system.
Using ctrl-shift-esc launches the task manager program without a system interrupt, meaning it won’t unlock the computer. Which is dumb, because why else would I be opening the task manager other than to interrupt some out-of-control process? I guess you could be using it to monitor or something else, but that’s what I’m used to opening the task manager to be doing. I didn’t even realize this until this comment.