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You are using bad the x-default annotation (I must admit, though, that I did not completely understood the code you copy/pasted in your question). The x-default is meant for showing to Google what URL to show to those users, who are not explicitly targeted by a dedicated version of the website. For instance, if we are targeting both USA and UK, but we know that the USA version has traction also in other countries like AU, NZ, South Africa and Spain, then we could use the x-default so to suggest Google that the USA URLs should be shown to all people independently of the language (in my example, not only English speaking users, but also Spanish speaking ones) and geography (not only the USA, but also all the others countries). The only exception will be the UK, because with the hreflang="en-GB" we are telling Google to shown the UK version of the site to English speaking users in Great Britain. The only solution I see in your case is consistency between the two versions. You must choose with which architecture option to go and use just that. Only after you should think in the hreflang implementation.