Doesn't really matter what you believe or feel. These are the current rules, and if you don't provide a valid offer of employment (where "valid" is defined by IRCC, not by you or me), you won't get the 50 points.
The whole point of the 50 points is to ensure that you have a job. I don't see where the possibility of a legal dispute comes up - if your employer is not willing to keep you employed, they will simply refuse to give you the letter.
If they are willing to keep you employed, they will give you the offer. Getting the offer doesn't mean they can't later fire you, or that you can't leave on your own once you're a PR. There's no binding legal obligation created by IRCC that affects you or your employer. A job offer is subject to all the usual employment laws, and there's nothing special about this offer that supersedes labor law. It's simply an indication from your employer that they would like to keep you employed - and therefore the Minister for Immigration has decided that people who have shown they will definitely have a job will get 50 extra points.
Nothing stops you from getting PR without the 50 points.