I've actually already read Gellar-Goad's article Don but sad to say I find it a little muddled and think we just need to accept the Epicureans we're wrong on this, they simply didn't have the tools we have. I think explanations of "real meaning" fall a little flat and remind me of how Christians explain Jesus failed apocalyptic predictions.
From my humble attempts at translating, I have never found a statement where Epíkouros positively says that the sun is a hot melon a few miles up. He never gives a definite size, suggesting that "the [Sun] in relation to itself, either [it is] greater [than] of that which is being observed, or slightly smaller, or [it is] as great as it happens to be." (Epistle to Pythokles 91). His thesis, as I read, is that astronomical objects are too distant to allow us to make accurate measurements.
(If disagreements in measurements between the JWST and the Hubble are any indication, we are still struggling over this point of contention, except on the scale of massive, cosmic filaments).
Even as a general observation, Epíkouros seems to indicate that the sun is "truly great", as he writes to Pythokles (so I've translated personally) "the size of both the Sun and of the rest of the glowers appears of such [great] size in relation to us [and] truly is so great" (10.91). Compared to other nearby objects, the sun cannot be easily "obstructed" behind a tree the way that a piece of fruit becomes completely obstructed. You need an eclipse; in other words, the only things big enough to block the sun other massive objects whose size we cannot accurately measure.
Also, just a quick side-note: we take "the size of the sun" for granted. It's not obvious. Consider neutron stars, which are the size of New York City, and can only shed heat on planets that orbit extremely close. Hypothetically, all this time of human history, prior to the 20th-century, the sun could have been a neutron star the size of New York City, and we wouldn't have known the difference.
I'd also like to add their context as naturalists and materialists. Epíkouros' personal philosophical hero was the naturalist Anaxagoras, who uniquely theorized that the sun was, at least, as big as a massive, geographical landmass (he names the Peloponnese). Further, having regularly sailed along the Ionian coast, Epíkouros (and the rest of the Ionians, I imagine) clearly witnessed mountains shrinking in the distance as they sailed, whereas the sun never shrinks. It would have been radically anomalous for Epíkouros to have suggested that the sun is smaller than mountains.
But he did get "heat" totally wrong. There are no "heat" particles. With respect, II think "the sun is a hot melon" is an attractive argument to opponents, but it is a colorful exxageration. There are plenty of other things Epíkouros got wrong that are educational points of comparison (like "heat").