And yes, I take it for granted that hyperbole is the explanation - what other possible explanation is there? Someone mistakenly using 'literally' instead of 'figuratively' - why would they ever have wanted to use 'figuratively' in such a sentence? It's clear to all parties involved that the statement made is, in fact, figurative and not literally true (except maybe if you're talking to small children or neurodiverse people who struggle to understand figurative speech), there is no reason to add that except for purposes of hyperbole. And the usage arose, not coincidentally, at the same time that hyperbole became more popular in all sorts of other ways too.

As for 'umbraphile', I wasn't familiar with the word, but then again the most recent big eclipse hype in this part of Europe was 25 years ago. So can't say I've thought about it before now - but as you, Greg and Joe have pointed out, languages evolve and all sorts of words or phrases that we now use without thinking were once considered incorrect or at least frowned upon, or have illogical etymologies.