I think the goal of mathematical notation is precision rather than ambiguity. Yes, the example seems awfully complicated for what simple thing it's trying to state. However, if you read it out loud it still sounds complicated. It's a simple concept, but it's hard to communicate without room for ambiguity.
How do we know if the solution they chose to achieve that goal is the most efficient one? How did that notation evolve? Has it evolved at all?
What if it's just a design by committee, with decisions made in the 17th century still affecting how modern papers are written?
What if we think of the rulebook on "how to write math" as a codebase? Would it be a 3-4 centuries old codebase without any major refactorings done, ever?
