Hi Kevin Thorne,
welcome to this Apple (user-to-user) Community!
Re: "So it seems that the heating test isn’t available in Canada either, so why does Apple show it on Apple Canada here "
We are all Apple users, like yourself in the community, so no-one here can speak for Apple.
Also, Apple does not always explain why it does the things it does in its announcements or documentation.
Seems to me the article you mention provides a way for those in Canada to check that linked article within it.
under "Here’s what you need"
ie: Countries or regions where the Hearing Test is available
Although Canada is not listed there as yet, it seems Apple updates the list if / when the relevant authorities in a country give approval for use of the AirPods / hearing-health features there. Canada may or may not be listed in that article eventually, so checking it now and then may be a way of keeping updated.
Canadians in other countries, or Canadian travelers, may also require information.from the two articles.
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Re: "this is misleading"
If you want to : You can send feedback to reach those who work on Apple's website:
Feedback - Apple.com Website - Apple