The main reasons for not issuing PPR/COPR to outland applicants could be:
1. Air travel into Canada is banned until at least 30 June (except for certain categories)
2. Canada may be making a policy of re-medical etc. to ensure that only corona-negative applicants enter into Canada
3. Unemployment levels lately spiked in Canada. Outland applicants on entering into Canada would either compete for already few jobs or seek aid from the government.
But why IRCC is not at least informing the outland applicants that their files are approved?
It may not be possible for IRCC to inform applicants that their files are approved until IRCC decides whether it needs a re-medical. Maybe the file is not technically approved until the re-medical is done. Anyway, IRCC is already working at limited capacity and wisely using its resources. IRCC will likely send only essential communication like PPR/COPR. They won't send any inessential communication like " Congrats ur PR is approved. Wait for PPR/COPR. We will send u PPR/COPR when the right time comes"