One reason why imports invoiced in local currency exhibit much less pass-through could be that exporters who price in local currency tend to be more concerned about preserving market share in the foreign country. They are prepared to absorb some of the higher costs associated with adverse currency moves to avoid passing them along to their customers.
A similar logic might explain the lower pass-through numbers observed on imports that come to Canada through a third country, such as the United States, as opposed to directly from the exporter’s country.