Since the overhaul (I think it was part of the major release of version 7?...maybe more recent) that made Notifications a type of Task under the hood (which, admittedly, made some other things far more versatile), if you want to refer to the task that caused a notification to be sent, you need to refer to the Previous Task, not the Active one.
Note that if you have jobs where a task can fail, and that means the job fails, but the job doesn't STOP at the failed task (I have some of these), a notification on failure at the job level will still report the previous task to be the last one that ran, which is no longer the one that failed. I have a few notifications that can be a little confusing because of this, and I really need to fix that, but because they only go to me I haven't gotten around to it yet.