Got the answer - after requesting passports, ircc sent to my husband a letter called 'Authorization for Exemption from COVID-19 Canadian Travel Restrictions' which he must present before boarding the flight, so immediate relatives basically can enter Canada as well with this kind of doc
We didn't apply for this authorization, but that's what the letter says - "Your request to be exempted from the current restrictions to travel to Canada listed in the Interim Order to Prevent Certain Persons from Boarding Flights to Canada due to COVID – 19, no.3, under section 3(1)(b) of the Order in Council, Minimizing the Risk of Exposure to COVID-19 in Canada Order (Prohibition of Entry into Canada from any country other than the United States) has been approved."
It also says "You must present this email when checking in for your flight, or you may not be allowed to board your flight to Canada. You must also present this email upon entry to Canada"