And they’d be starting and stopping all over the place, so the kind of acceleration needed to reach that speed would kill any known organic being via g forces before they’d even suffer from the fire. But he’s one of the fae, so data on them is lacking I guess.

cardiomegaly leading to diastolic heart failure more than likely

As you say in your first sentence, language is by consensus. And, the long-standing consensus among ichthyologists is to use exactly this terminology, and you’ll find it consistently across the scientific literature for generations now.