Is it? By the time it's in the US (i.e. there is TSA around) it's getting off the plane not on. Why would they bother? Why would they have a pipeline to proces

Is it? By the time it's in the US (i.e. there is TSA around) it's getting off the plane not on. Why would they bother? Why would they have a pipeline to process such luggage? (Of course it's presumably scanned by the Canadian security in Toronto... just not the TSA).