Apologies for the delay in responding. I felt it would be wise to read Rovelli's book for myself first, to try to get a sense of exactly what Kastrup's contention with him is, before trying to unpack my intuition here. I have my own issues with Rovelli's perspective, in that he seems to fundamentally misunderstand the Hard Problem, but in terms of the (lack of) Ground, I think I can stand by my initial reply, which is that I don't think the dispute amounts to much at all. Kastrup likes to say of his Ground, his Mind at Large, that just as ripples on a lake are nothing but the lake, or the vibrations of a guitar string are nothing but the guitar string, so the patterns of excitement of M@L are nothing but M@L. So far so good. But then what is M@L without its patterns of excitement? What can we say about it? It seems to me that we can say nothing -- it is the unrealized disposition for patterns of excitement, but an unrealized disposition isn't anything at all.
To say, with Rovelli (as he says with Nagarjuna), that underlying the mutually arising world of things is nothing is, at least as I see it, to say exactly that: there is nothing that the Ground is, and if there is nothing that the Ground is, then the Ground is nothing, and I don't see "The Ground is nothing" as meaningfully distinct from "There is no Ground." So there is no Ground. Kastrup is wrong. But... on the other hand... while M@L without its ripples is nothing, M@L is not without its ripples. It is rippling. Or, per Rovelli, we might say that while a relational reality without any actualized relationships is nothing, in fact, relationships are actualized: reality is relating. Hence, the disposition underlying those relationships -- the fundamental relatability itself, or M@L -- is realized in the relationships themselves and reveals itself in every revelation of every relationship or being or ideation or what-have-you. So there is a Ground. So Rovelli is wrong.
The conclusion that seems unavoidable to me is just this: mutual arising extends even to the relationship between Ground and contingent arisings in/on/through the Ground. The eternal and the temporal constitute one another. The Ground of the world of relations only exists through the relations it grounds, which only exist or cohere through it. They are not two. So when Rovelli brackets the world of things-in-relation and sets it aside and, without it, goes on the hunt for that in which it's grounded and finds nothing at all, he hasn't missed anything -- there's not anything for him to miss. He's not wrong. But when Kastrup looks at the world of things-in-relation and, through it, gestures at that in which it's grounded, he isn't wrong, either. As Lou Gold said in their response to me, form is emptiness and emptiness is not other than form. This, I suspect, is what Nagarjuna meant when he said that even emptiness is empty, and if it isn't, then, at least, it's what I would mean by his words.
So to answer your question directly, yes to all three: the distinction is meaningless, because it's a distinction without a difference or, at most, a quirk of the particularity of perspectives; the concept of "no Ground" is meaningless because there is nothing to deny in the concept of "Ground" apart from its arisings; and the Ground of being and the being of beings reveal themselves as, well, interbeing.