Pedantic.

> A narrative is a structured account of connected events, experiences, or ideas, commonly referred to as a story

Regardless of intent, it is how you tell your story.

I don't think the comment was intended to be pedantic, but rather to reframe the message as scientific fact.

I think you misunderstood. “Narrative” typically frames something as polemic or open to interpretation, which this is about equally so to the whole “spherical Earth” story.