The choice to support DNS roots like .oz, .ku, .te, .ti, and .uu is not standards-compliant. Say suddenly a new nation comes into the world and ISO assigns them one of these abbreviations, or one of these “emerging countries” they have TLDs for gets assigned a different cctld, what does opennic do? They made the choice to pre-register a bunch of domains under these reserved 2-letter country codes, so now they either have to
A. stop being able to say “we directly support all ICANN-assigned tlds” and keep resolving the existing domains
or
B. say to the existing domain owners of [their artificial] tld “sorry to be you” as their domain names they thought they owned now become registered to other entities.