Peace,
Since I was the originator of this theory I will offer my logic for it. However, I must add that i have since rescinded my opinion on this, as I have come to terms with a purely lunar pre-Islamic calendar that includes Ramadan and a separate solar calendar that was used in pre-Islamic Arabia based on the constellations.
My premise first started off on the fact that the text of the different readings of the Quran that we have do not consistently reflect the tajweed employed when they are recited. With that first established I began to study the phrase shahru ramadaana. My first idea was that the raa in ramadaana can be read with a shaddah (a tajweed prounciation that is not consistently reflected in text). Reading this with a shaddah would automatically imply that shahru was not just shahru in an idaafah construction but rather shahrun with idghaam. This idghaam consisted of the assimilation of the noon into the raa' of ramadaan. Again these specifics are based on the premise that the rules of tajweed are not accurately represented in Quranic texts, and that this was a reading that most recitors did not take because of their traditional reading traditions.
As for ramadaana, there are plenty of places in the Quran where the rule of adding an alif for accusative or having alifs where alifs do not usually go are broken. That is because the traditional texts as we have them reflect the development of Arabic writing conventions and are not the end product of writing conventions that were agreed upon after the Quran began to be written down.
Anyone who pays attention to the written texts of the Quran and doesn't just assume that they follow all of the writing conventions that are taught will see that the Quran shows us different stages of wiriting conventions as Arabic was being developed and standardized as a written language.
These are the reasons behind the stance that I took before about shahru ramadaana. Again, I have rejected my previous understanding of the phrase based on having come across evidence that the pre-islamic calendar for hajj and ramadan was PURELY LUNAR.
Godbless,
Anwar