Deja vu and dreams are different entirely, as they are different from past life regression. PLR is not something that is triggered as I'm sure you realise, it has to be the subject of the hypnosis in the first place. It is also easy, as you pointed out, to falsify this by guiding the subject through the process, but if done without prompting at all then that is different.
Now future life progression is something we haven't addressed in this thread, and I think it's possible this is what happened to you in some way.
I have heard the same thing about dying in a dream, however I was run through with a sword in a dream and it was a weird feeling. I think it could be described as feeling your life draining out of you.