The National Post are not experts, and they aren't reporting what experts say accurately. And while there's a video in there where an actual expert speaks,
you're not reporting what that expert said accurately.
Public health officials, while they usually are experts, have other concerns beyond simply saying the truth. The US and Canadian recommendations against medical masks for the general public were part of a strategy based on reserving medical masks. So yes, you should have followed the recommendations of health officials and not worn a medical mask, because healthcare workers needed them.
As far as I know, neither the US nor Canada has ever taken a stance against non-medical masks. They haven't taken a stance for medical masks either, but this was likely due to concerns that people would be confused about medical versus non-medical masks. Your own post is an example of this being a very legitimate concern: you have completely failed to differentiate between medical and non-medical masks.
If you look at what experts have been saying who aren't part of governments, the messaging has been fairly consistent: masks prevent illness at varying rates, and we need to prioritize healthcare workers when allocating the most effective masks.
So when you say, "Should I have deferred to expert opinions and waited until yesterday(!?) to start wearing a mask?" I have to say, no, it would have been impossible to do that, because deferring to expert opinions and waiting until yesterday to start wearing a mask are mutually exclusive actions.