I was actually dumb enough to put my overseas address in my original application. They can't even look up a physical presence through border control records by themselves, because they keep asking people for copy of passport pages with stamps. They would never know if I had not told them.
Some Reminders:
Obviously an applicant for citizenship ABSOLUTELY needs to give accurate, truthful information in the application, including the address where they actually reside. What would be dumb, taking a big risk, is to do otherwise. Seems quite a few are dumb enough to take such risk.
IRCC primarily relies on the one best source of an individual's travel history: the person who for sure was there each and every time the PR entered and exited Canada, that being the one and ONLY person in the whole world who can for sure make and keep a record of every entry and exit. That is, the PR applying for citizenship.
IRCC will cross-check the applicant's report of travel history in multiple ways, using various sources of information, including CBSA travel history. If discrepancies or other reasons for concern are noted, that will cast doubt on the reliability of the one best source, and could make it very difficult for the applicant to meet the burden of proving their physical presence.
Among examples of information that passport pages might be examined for is to see whether there is any indication in the passport the PR obtained status to work in a country that might be inconsistent with the work history they have reported.
Otherwise, and Overall:
IRCC typically knows far more about PRs than what many apprehend. The extent to which many get away with false information can be misleading. Many, and it's probably a safe bet that most who give false information are caught. The consequences can range widely, from just a minor compromise in the PR's credibility to outright prosecution for misrepresentation.
It would be foolish to tempt fate on that very slippery slope.