Do I read your question right in that you interpreted the sentence “Don’t rush, you may fail” to be a thread?

Yes, looks like they are putting too much pressure on me and because of their pressure, I am about to lose a postdoc job.

Can you ask them more precisely how they see your work up to now, what they believe the chances of failure are in the current state, and what still needs to be done in their opinion?

"Has anyone ever failed the PhD defense?" Why are you surprised? It is an exam and you can pass it as you can fail it. Usually, a supervisor/PhD committee does not let a potentially failed dissertation be defended unit meeting the minimum requirements. These requirements should be discussed with the student before starting. However, if they are not met, the student shouldn't defend or fail and I don't see room for social work because of another offer (sorry but this is the truth). You should work on what remains in your PhD and do not get confused with other job offers.

I can't add much to the existing answers, but the comment reads to me like "You need to 'ripen' a bit first". I don't see a threat. I see good advice. Jumping the gun isn't wise in foot races either.

"I am a final year PhD student" this qualification can only be known retrospectively ;) (best of luck)

What's your current plan/timeline? I.e. when you you plan to be done with your thesis, how long do you think the defense will last, etc.

Did you have some sort of Senate or Qualifying Exam where you laid out a proposal that your committee and supervisors accepted? And did you complete all that work?

It sounds like there is an implied solution to the possible failure: not rushing.

In a different question op states he has a postdoc lined up. Maybe the Better question is if it’s normal to fail a defense in such a situation. In my field this would indeed be weird, as getting a postdoc is viewed as a good sign that one is ready to pass the defense. Though I think A.SE already has a few questions in the vein of “I have a postdoc lined up, but my advisor is getting in the way. What to do?”

@shalop But in the same question (from two days ago) the OP also says that they intend to start writing their thesis after finishing a few other things. If you haven't started writing your thesis yet is it reasonable to conclude that you will be finished and done defending it in less than 4 months? The supervisor doesn't seem to be saying that it can't happen, just that they don't want to promise that it for-sure will happen.

@hobbs Money? ..

It seems like the OP is imagining that they have a postdoc job, which they are "about to lose". This is false. They only have a postdoc offer conditional on the completion of their Ph.D. That the OP obtained such an offer in a situation where it's not clear whether they will in fact complete their Ph.D. by the given date is the OP's problem. In particular, no-one is obligated to let them successfully defend just because they have a postdoc job lined up.

I know people who failed. They got a masters even if it was a second masters.

I just need that degree, that’s it. After that, who cares what I do. I can go and work as a waiter, why does my silly supervisor care? Another reason is: I am very unhappy in Canada so I need a way out and I found a perfect way out. My supervisor is blocking me.

Also, the same silly supervisor keeps on telling me I am good and I should not have problem finding a job after. Then why the same silly supervisor is telling me I can fail?