I find this step very cumbersome and somehow superfluous. What this innovation brings could already be solved via shortcodes. Why should I install a new plugin? Superfluous!

I think this is just an answer to the despair of the whole Page Builders. There is no clear answer to the question Gutenberg asks.

Phase 2 and the comment of @alexislloyd are even more interesting:

I would also suggest that we refer to these as "complex blocks" (i.e. blocks containing multiple blocks to achieve a common pattern), to distinguish them from "simple blocks" (blocks that contain only one block) and from "templates" (which apply to the entire page layout).

The future will be interesting.