"In no way is Canada Post privatized by any rational definition of that word."
According to the definition you posted (I bolded the passage) that seems like a fairly straight forward rational definition?
By establishing Canada Post as a Crown corporation, is in many ways similar to what was done to the USPS when it was taken 'off budget' meaning that it was no longer being subsidized with taxpayer money. And while the Crown (govt.) is still the sole stakeholder of Canada Post, it allows it to operate at arms length. To the point that Canada Post is able to invest/purchase wholly owned private companies like Purolator Courier to own at present a 91% stake in it. So in many respects, it can IMHO be argued that Canada Post is more privatized than nationalized. And the fact that there have been numerous strikes and service disruptions, also places it functionally and operationally in the realm of a private corporation.
There are plenty of grey areas to go around no doubt. For instance in the U.S. the major rail freight companies are 'private' companies although they are publicly traded in the stock markets etc; And while they are also able to strike, the govt. can and has stepped in during the past to order them back to work. In much the same way that the Canadian Parliament is stepping in to order Canada Post back to work.
In the USPS, they are still nationalized in the sense that they are prohibited to strike or otherwise inhibit the service, whereas Canada Post shares more in common with privatized corporations in that crucial regard.