They can come back and use Canada health care without paying a dime for it while living outside Canada. They can stay out of Canada until they get a serious illness that will cost them serious money. So they can come back to Canada and get coverage right away if you go to Alberta.
I had a conversation with one person who was born in US to canadian parent, never lived in Canada. Just moved to Canada so he can sponsor his American wife and stay long enough for wife to get Canadian citizenship. Once wife gets it, they will move back to US. I believe he wants his American wife to have Canadian citizenship so that she doesn't have to worry about medical care cost in US. If one of them get cancer, they go to Canada to get free medical care. They won't have to worry about selling their house to pay for cancer treatment or any costly treatment.
If that is not called "Canadian of Convenience" I don't know what is.
If our medical care has followed the US format whereby everyone pays for their own care, then there wouldn't be any Canadian of convenience since tax payers would not be on the hook for their medical cost.
As long as there are services paid by tax payers, medical care, OAP, etc, there will always be canadian of convenience out there taking advantage of it.
In conclusion, "Canadians of convenience" is reality, not a made up word.