That is a conspiracy theory that can easily be disproven if you look literally anywhere outside of Western Europe. Muhammad started Islam and composed the Qu’ran at the beginning of that time period, and the Islamic calendar begins in 622 AD. According to the Phantom Time theory, basically none of early Islamic history actually existed and it’s a fabrication by… The Pope?! It’s an absurd premise. The Abbasid Caliphate was founded in 750 and still existed in 911, with all sorts of written and archeological evidence in favor, and let’s not forget about the other Roman Empire that existed in that time frame and have their own historical and archeological evidence, including about events that overlapped with Western histories such as Irene of Athens being pressured to marry Charlemagne. Again, it stretches credulity that the Byzantine Emperors and Eastern Church or any Muslims whatsoever would be swayed to fabricate so much of their own history by the Pope. This theory is absurd at best and racist at worst because in erasing so much Western European history it just kind of assumes literally nothing was happening anywhere else in the world either.