Another thing to add about the reason why 4-year requirement wouldn't be unreasonable:
let's say someone accumulated 1095 days over the course of the last 5 years, but spent over 183 days in country A 3 years ago and committed some crime or even stayed in jail in that country, not requiring police certificate would let him get citizenship with no issue, is that really what we want?
To be clear, all applicants must affirm the absence of any prohibition. There are no changes to the time period covered by the prohibitions. This is and remains four years. Any conviction (for what would be an indictable offence if committed in Canada) abroad within the preceding four years means the person is prohibited from a grant of citizenship. Not eligible. And there is no way that IRCC is going to drop the prohibitions item from the application.
So a person with a conviction within the preceding four years will not be eligible. If that person fails to disclose this, that is a material misrepresentation. This is precisely the kind of misrepresentation which has historically (in addition to war crimes) been the target if not focus on revocation proceedings. (Noting though that prior to Bill C-24, there was no citizenship prohibition for a PR's foreign convictions.)
Moreover, the prohibition is not triggered by 183 days in other country:
The prohibition is triggered by a conviction in another country during the preceding four years. Even if the PR was merely transiting another country, committed an offence, and was convicted there within the preceding four years, the PR must disclose this in the application. A failure to do so is a misrepresentation. No minimum amount of time in that other country is necessary to trigger the prohibition.
Again, the 183 days within four years criteria, for triggering who needs to include a police certificate with the application, is
ADMINISTRATIVE, not dictated by statute or regulation. IRCC can change this criteria (as long as it is reasonable) anytime. IRCC could require anyone who spent 30 days in another country to submit a police certificate. Or increase the triggering number to 200 or 300 days. Or drop it altogether.
And regardless whether or not an applicant needs to submit a police certificate, a conviction during the preceding
four years will still constitute a prohibition.