Agreed...especially your very last sentence.Again, a thing that I believe was covered elsewhere in this thread (but at least another) - when you make a request to one agency (eg IRCC or CBSA), the request may or may not include information that the agency can get access to but that it does not 'own' - meaning usually information created/owned by some other agency.
Upshot: you may not get all records of entries and exits from CBSA - just not certain.
So yes, you need to keep your own history.
The CBSA agent/officer that I spoke with yesterday said that they do NOT record exits from Canada, he said "That's only recorded when you go through Customs." Huh?
While I do understand that the information is not all-inclusive, at least between agencies, I would expect CBSA's records to be the most accurate, since that is the agency that is, in essence, `the doorman/bouncer' for those seeking entry into Canada. I suppose CBP is the other doorman when exiting Canada, but their records may be even less accurate.