There's a couple of things that may have affected my experience: it's been ages, over 2 years, since I've bought through Kobo so I can't say for sure but I'm thinking the ebooks without the download symbol were probably bought through Kobo US. I wasn't aware there was a Kobo Australia and I don't know when that started as a separate space.
Also I don't use a Kobo ereader (someone who shall remain nameless put their elbow on the screen years ago).
And in the end, all said and done, I decided I didn't need an app that wasn't consistent when the website works fine. When I do buy from Kobo I'll just use the site.
And it was the advice from the customer service people, something I found quite funny, I usually expect such companies, after trying to solve such a problem to blame the customer in some way