I find it interesting on two fronts. First, the Canadian GST/HST changes causing this were in place effective July 1, 2021. I haven't looked at whether ebay is just slow or somehow got an OK or fit some exception for the delay (not sure on the provincial side of their exact date changes).
Second, there have always been self reporting rules whereby, if you were not charged sales tax for imports on personal purchases, that you were supposed to self assess and pay the sales tax directly to the government (so the whole work around by buying from sources outside Canada that don't charge sales tax doesn't technically work). Almost no one does this self assessment of course.
Third - on a quick read, it looks like eBay commissions, being based on total sale price, including the sales tax, means there is added fee to the seller, just because of the sales tax being charged. I don't sell on ebay, but thought that would be useful for sellers to know and look for / confirm