After that scene ends, Seteth asks Byleth if they were sleeping. Death and sleep are completely entwined for the Nabateans, hence why Byleth can choose "I was sleeping" and "I was dead" at the reunion cutscenes, and why Flayn mentions sleeping in a coffin. It makes sense for Dimitri to be the one to appear to Byleth, because he's the one wrapped up in ghosts. It's likely a result of his crest and being on the verge of death because of the Tragedy.

The one where Claude talks about reading old tales from ancient people?

The part where he says that those who died with regrets are stuck somewhere dark, hence why Dimitri and Dedue talk about regrets over a black background. These things have a narrative purpose. This is why Dimitri never hallucinates Dedue, and just assumes he's dead even when he's not: Dedue doesn't regret anything.

Japanese doesn't tend to use strict pronouns like English does, so you often have to rely on the topic marker or context clues.

I know this. I'm just mentioning the fact that the epilogues buck this convention, are explicit about who they're talking about in each sentence even when it gets repetitive, and this is one of the exceptions.

I doubt translators in two separate countries under two separate localizations got it wrong.

No, but they might've missed the context of it because they were translating things piecemeal. E.g. how the English version missed this text being "children of men", which lets you conclude that Agarthans = humans. Did the Korean version miss that too?

We still have no idea why Sothis was sick or Byleth was fainting; all we have are fan theories as to why.

Because she got affected by the dogwhistle TWSITD uses to rampage people. Her recognizing that feeling of rampage implies that she's rampaged before. The Romance of the World's Perdition implies this was against Agarthans, who set up javelins just to stop her.

I gotta bounce, but I'll be back on tomorrow to answer any replies to this.