Your understanding of canonical tags is correct, GhillC.

If Tools are showing errors for those canonical tags you've listed, then the tools are wrong.

As long as the protocol and subdomain prefix (or not) exactly match and the only difference is the exclusion of the parameters (the "?" and the stuff after it) then the canonicals are correct.

Any tool's reports have to be filtered through your own understanding and knowledge. They often get things wrong. That's on eof the key differences between experienced SEOs and less-experienced. They kow when to question what an automated tool is telling them. So good on ya for questioning the results!

Paul

Actually, no-indexing your contact page is usually a very bad idea, especially if you are depending on any aspect of local SEO for the site in question.

You Contact page is the ideal spot to include all your geo-location information, your properly formatted NAP (Name, Adderss, Phone) to match your Local Citations, and a Google Map of your location.

As the others have said, even if not depending on Local SEO, there's no value to just no-indexing this single page.

Paul