That is certainly how IRCC has handled it in the past - if you lose your job, you lose your 50 pts, before or after you submit your eAPR (lock-in date). There have been cases where people either changed jobs with a new LMIA, or lost and then found a new one during processing, and IRCC accepted that.
I agree that there is more ambiguity now than in the past in the information presented by IRCC - for example, the page on job offers was just updated on 2019-05-15, and the information that used to be there about the job loss and loss of 50 pts has been removed.
https://www.canada.ca/en/immigration-refugees-citizenship/services/immigrate-canada/express-entry/documents/offer-employment.html
However, it is still in the Ministerial Instructions:
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/mandate/policies-operational-instructions-agreements/ministerial-instructions/express-entry-application-management-system.html
"Loss of offer or inability to perform duties
(3) If the offer referred to in subsection (1) is revoked or ceases to be a qualifying offer of arranged employment or if the foreign national is unable to perform the duties of the employment or is unlikely to agree to perform them, the foreign national is no longer entitled to the points assigned under subsection (1) in respect of that offer and the total number of points assigned to the foreign national under the Comprehensive Ranking System is to be adjusted accordingly."
I am wondering if there has been a court case (if so, I haven't found it yet, it might be pending) about the apparent contradiction in rules pointed out earlier in this thread (where changes after the lock-in date should only be considered if they affect program eligibility).
In any case - Unless/until the Ministerial Instructions change with a program update, however, I would expect IRCC to continue handling the loss of job offers the way they have since the inception of the Express Entry system - you lose the points and possibly your ITA.
So, if you lose your job offer, do your best to get a new one as quickly as possible -