They already are inviting people from other countries - for example the applicant who got PNP from outside of the country. So per your rationale, they are already "importing" Covid from abroad.
In my opinion (which obviously does not matter whatsoever), they can wait out the peak (which I think is what they are doing), free up healthcare capacity, test everyone arriving and determine quarantine actions based on individual test results (positive people quarantine in hospitals/other facilities and negative people self quarantine in homes with added oversight).
From a Covid perspective, the biggest risk for Canada is the US. If they view it from an "importing Covid" standpoint, they should be closing the Canada-US border longer than closing the border to Brazil and India. Closing borders with the US will be a bigger economic impact which will in turn lead to a political disaster. Also, opening borders does not directly equal Covid clusters (thereby resulting in a political disaster) if performed mindfully and safely. However, I agree - the risk exists but can be mitigated.
I am not sure if it is even legal to restrict FSWs to a certain country (the legality of this has to be verified) and not sure if it aligns with the purpose of the stream.
I am guessing that FSW will resume (maybe with additional Covid related requirements upon arrival to Canada) once they are confident to open borders for international travel.