It’s not really about the expectation, though cutting to Finn for a split second does feel odd, it’s more about that series of statements.
“I had a vision. Of the throne of the Sith. And who was on it. And me.”
The first two statements make clear that she had a vision about the throne of the Sith, and the third statement clarifies that she saw someone on that throne. The fourth statement however doesn’t make it clear at all that she saw herself on the throne, rather that she had a vision of herself separate from the throne, since the ‘and’ implies that her presence in the vision was not included in the part of the vision revealing the throne.
She could say “I had a vision. Of the throne of the Sith. And who was on it…me.” This would confirm that she was on the throne and not separate from it.
Or she could say “I had a vision. Of the throne of the Sith. And me.” Which merely implies that she is on the throne.