You can't without using PKHeX. The Luma/NTR region changers only change the 3DS region, not the sub region so you end up with pokemon with mixed geolocations I.E 3DS region (whatever you chose) sub reigion (your actual sub region) and the country is left blank. The ONLY way to fix it is to do it manually, I just export the save change the region manually, then receive my pokemon and everything is correct.
The EventAssistant also sets the correct sub regions and doesn't require region spoofing, only language changes which is done in the app itself as well ont he fly without exporting anything.