@Edent There's a whole bunch of "free" QR code generators out there which automatically run things through their own link shortener.
A friend got caught out when they found that after a week their QR codes were disabled because the redirector wanted money from them.
It prompted me to throw together https://dorward.github.io/qr-web/ - it took me rather longer to write the rant than it did to write the JS (and I've just updated it with a couple of links to your blog as its an excellent reference).