Of course they're sources, and of course it's recent theory. Did you think this was gonna be something explicit in Yerushalmi, or in rishonim, and you'd never heard of it till now? It's an interesting historical theory, with no real bearing on any practical matter. Don't know why you seem bothered by it.
It's against straight forward Chazals as they have been traditionally understood for centuries. I have no idea what great kasha this theory is coming to settle either.
Not enough? All the lessons we have been taught about nohagu kovod are based on a cover up? I don't like it, and definitely don't buy it.
I have no idea what the motive to turn the tragedy into some kind of heroistic lost battle was. As you said, it has no bearing on anything, besides that they are taking Chazals "with a grain of salt" (CV).