thank you for your comment. And I understand what you are saying: there are various cases (retirement is just one of them) for which a non-o visa might be issued. But it does not really answer my question. Why would there be more than 1 visa category (non-o vs non-oa/x) for one and the same purpose (retirement)...?...and even more confusing...why would there be different requirements applicable for the same purpose (retirement)...non-o (no insurance needed) vs non-oa/x (insurances needed). So, if non-oa is no sub-category of non-o, then at least one would expect that very soon another order will be issued also requring retirees under non-o to have an insurance.
I am struggling to fully understand the dogmatic which underlies non-o, non-oa and non-ox visa category: if non-oa and non-ox are NOT SUB-categories of non-o but separate own categories of visa, then one could apply for a non-o visa based on retirement and by this, maybe, "escape" the insurance requirement which sounds odd to me. Also if non-oa and non-ox are NOT SUB-categories of non-o, then you would have with non-o and non-oa two (partly overlapping) visa categories for the same purpose (retirement). This sounds also odd to me. Maybe I misunderstand something here? Perhaps someone could explain this to me?