You need to prove current persecution so if you haven’t lived in another country for a long time it becomes much harder to prove that you still risk persecution and that there are no safe locations in the country. If there is conflict in the country throughout the whole period it is easier to prove that the risk to your life remains. Canada was seeing a movement of those who had settled in the US claiming asylum in Canada and started to intervene more. We also starting seeing the US refusing visitor visas more often to those who had come from the US and claimed asylum in the Canada. We now know that Canada has been trying to close the loophole in the safe 3rd country agreement for at least a year but likely a lot longer. There are more subtle way that both countries were trying to discourage the movement of asylum seekers from the US and the misuse of visas. Minister rarely intervened 5-10 years ago for those who had been living in the US and that was no longer the case before the safe 3rd country closed.