Rohan is an Unreliable Narrator.
Either Rohan is exaggerating his positive qualities while retelling his stories and, for example, impersonated a priest on purpose or didn't even come close to being able to compete with Yoma Hashimoto, or his stories are all made up. Kushagara is banned from the world because it replaces other words with itself
The word itself devours other words in order to multiply. If it were allowed to exist it would begin replacing every word it comes across with itself, including words that aren't actually printed such as spoken or thought words. This would render anything it comes across comatose and result in a Death of Personality. Even worse, it may be capable of rewriting a persons pages that can normally only be viewed by Heaven's Door which would result in their entire history becoming nothing but Kushagara thereby warping reality to the point that the person infected becomes the actual word. Episode 1 Will Feature a Major Twist
With a reveal in Part 9 that an unusually identical Rohan exists in the SBR universe, the Part 8 Morioh landmarks in Thus Spoke Kishibe Rohan retroactively imply that the series has been set in the SBR universe at least since Episode 6. What if, then, the real reason the episode order has been so strange is related to the different continuities, and the continued lack of a first episode might address this? For instance, what if the first episode reveals that both Rohans are the same guy and show how he passed from one universe to the other?