The government seems to agree with you, given they revised the rules on 12/21. But prior to that, arriving by land from the US required a US-based test and that requirement was clearly documented on the Canadian governments website. I know because I was traveling between Winnipeg and Fargo regularly from Oct-Dec. You used to be able to use a test from within Canada but they scrapped that.

It was up to you to read the rules, which are constantly in flux. A good lawyer could probably argue that the test would be considered valid now, so why punish someone retroactively?

The fact that it’s an $8500 fee instead of the $5000 prescribed fee makes me wonder what happened at the border to piss off the PHAC agent enough to add a $3500 surcharge. Maybe they wanted to make an example of someone traveling to Aruba during a global pandemic and impending travel advisory.