That's the boiling point at atmospheric pressure. The NaCl we observed is likely not that hot - probably only ~100K but maybe 1000K (fig 6 of https://ui.adsabs.harvard.edu/abs/2019ApJ...872...54G/abstract shows that there's some ambiguity - we measure two temperatures and are not sure how to reconcile them!). We observe NaCl in an effective vacuum, so the boiling point (more likely sublimation point) is much lower. That said, it's possible that non-thermal mechanisms are responsible for releasing the NaCl into the gas phase - in other words, the gas isn't at the boiling point, but something knocked the NaCl molecules off the dust grains. Another possibility is that individual dust grains got very hot briefly, hot enough to vaporize, but again the gas isn't all that hot. We don't know for sure; we haven't yet come up with a consistent model to explain all the observations.

Just to give you a sense of boiling points: water transitions to gas at 373 K at atmospheric pressure. In the interstellar medium, it sublimates at closer to 100-150K.