Maybe I was being too generous to your post. There is no way to decouple GDP from material inputs, even if, as with digital good and services the inputs are quite small. They're still there, which means they're still finite, which means GDP is finite.
So perhaps the issue is that there are two cases being conflated.
In the practical sense, there is ample room for GDP growth on Earth in the immediate future. A huge portion of the population is underdeveloped while only a fraction of the world's natural resources have been extracted. Data also suggests GDP in developed economies can be increased while total resource consumption decreases once areas reach.
If someone is going to make a hypothetical mathematical/universal scale argument, I think it worth pointing out that GDP is accounting construct, with no inherent tie to material reality. For example two people could sell each other arbitrary services, (eg silence), and charge arbitrary sums.
