I'm not familiar with a lot of the acronyms and catch-phrases already in the first part of the article... let me try to make a bit of sense of this:

  IR = Intermediate Representation
  SSA = Single Static Assignment
  CFG = Control-Flow Graph (not Context-Free Grammar)

And "sea of nodes" is this: https://en.wikipedia.org/wiki/Sea_of_nodes ... IIANM, that means that instead of assuming a global sequence of all program (SSA) instructions, which respects the dependecies - you only have a graph with the partial order defined by the dependencies, i.e. individual instructions are nodes that "float" in the sea.