No one really knows how this is going to work. However, in the link that you provided, it is clearly declared that they are ONLY processing some specific applications and our PR applications are not one of them.
See the link below, it gives more detailed information:
https://www.canada.ca/en/immigration-refugees-citizenship/services/coronavirus-covid19/visitors-foreign-workers-students.html
more importantly is this following:
"If you’re travelling to Canada from outside the US
You must be
both
Exception: An
immediate family member of a Canadian citizen or
permanent resident who is staying in Canada
for at least 15 days is exempt and can travel to Canada for
any purpose."
So our immediate families do not even need an essential reason to travel!
About the documents, they only need biometrics and if you have already done it for your PR application, you don't even need that. What remain is just a couple of forms, invitation letter, purpose of travel, proof of relationship and financial support. Add to it a 14 day quarantine plan.
All these being said, I do not know how it will go but I applied. Also, there was a deadline to apply under these circumstances which was June 30. I do not understand why and if they have extended it.
It seems they are finally planning to start doing some work but still not clear to me. I am in my 12th month and still waiting for the medical!