QR decoding is beyond me. Also, is the information in the QR code the same are the information in the bar code? Maybe it's the barcode that includes the IOSS number? But as I said, if Joe Bloggs could decode IOSS numbers from postal labels, that would be a *bad thing*.
Are you talking about the 'Pre Reg Tax Scheme' box on physical label? If you are, then no, the IOSS number shouldn't appear there. If that was your own unique IOSS number, would you want it displayed on every CN22 label you created? Because you need to keep that number safe, else some fraudster uses it.
Good spot, maybe it does refer to IOSS numbers *not* sent direct from marketplaces, though that certainly isn't clear on the page. But the logo would go on the postal label if it's going to appear anywhere, not the CN22.
Regarding verification of IOSS numbers, postal services don't have any part in that - it's done by customs. So who knows why your label didn't have a logo. It might be that the C&D IOSS logo thing is just broken at the moment.