the Dutch do that because Canada was where their Royal family fled to during ww2. And Canada played a huge part in liberating Holland.
Canada and the Netherlands have a special relationship resulting from actions during World War II when Canadian forces led the liberation of the Netherlands and hosted the Dutch Royal Family in exile. The special relationship is still visible today, with the Canadian government describing the Netherlands as "one of Canada's most significant trade, investment and innovation partners."[1] In part, the Canadian Tulip Festival still commemorates this relationship.
In 2019, Dutch Heritage Day was proclaimed as being on May 5 each year in Canada; coinciding with Liberation Day in the Netherlands.[2]
https://en.wikipedia.org/wiki/Canada%E2%80%93Netherlands_relations