Unclear why this is special. Does it fly along the path, extending it? Is that feasible?
There is definitely a possibility of there being cloud cover, even at FL300, to cover the path of that flight. Assuming they would be allowed up to fly above FL380 by ATC, even less likely, but still not zero potential.
A major part of the eclipse experience is observing its interactions with the world. There's no much world to interact with at 30K feet, besides one big shadow.
This seems like a thing where the main value is that it costs more and is less accessible, so you can brag about it.