Yes, that is absolutely true but as we know, immigration sometimes refuses cases based on bogus reasons. If the PR in question had sponsored his spouse for PR and immigration finds out, possibly when trying to contact him that he has actually been outside Canada for the last few months, they will likely deny his application based on him not residing in Canada. Legally he might still be residing in Canada and of course he can appeal but I'm only saying, maybe you are better off trying to avoid having to appeal. It is safer to make short trips only so that the visa officer will have no doubt that the person is residing in Canada and not leave it up to the visa officers definition of how long you can be away to still be considered a resident.