I think what is particularly exciting about Gutenberg is that everything serializes to HTML. I’m not sure exactly where Full Site Editing is at the moment, but it looks like it might also be something that can be serialized to HTML. But in a manner where we can say which bits are dynamic and which bits aren’t.

So I think a particularly exciting form of Jamstack is not completely API powered by structured data, where you re-implement your block styling. But one where Gutenberg does the compilation and rehydrating of bits that need to be dynamic.