With all due respect but I think you are wrong. It's actually very simple
1) We buy an unlocked phone, so it has to work with any network
2) LTE becomes available, but we aren't able to connect to it so we suspect Proximus.
3) We contact Proximus and they all say they did everything they could, and Auka confirmes it here.
4) The problem is caused by Apple. They should solve it, because it is the law.
And we're now waiting for the solution. We know by now that Proximus isn't a supported carrier, you've said it a thousand times by now. But we have bought unlocked phones, they have to work. And like we said a thousand times: it's the law. If Apple doesn't respect that law? Fine, except that they will get a ban to sell their phones in Belgium (and posaably even the European Union). And i don't really see a reason why Apple just wouldn't release a carrier update. Maybe they don't have to serve Proximus, but they have to serve their customers (we). I believe it's just a matter of time.