The fact that your sponsor claimed asylum and got their PR based on their asylum, they shouldn't have returned home at any point. CIC now thinks that your sponsor lied about their asylum claims in order to obtain PR. It doesn't matter if they travelled on a Canadian Passport, a refugee cannot go home once they claim asylum. That's the whole point of the refugee process.Sponsor never visited home country when he was PR visited after citizenship and I think that is not considered as misrepresentation
If you apply as a refugee in Canada, you should expect to never go back to your home country regardless if you are a PR or Canadian Citizen.