But that's my point. You don't _need_ a formal grammar to make statblocks that are readable by people.
Yes, we do.
Here's a real-world example of why: My program, DM's Familiar, can import stat blocks. As long as the stat block follows a standard format, my program can import it. Where might a stat block come from?
It might come from software: PCGen, E:Tools, etc.
It might come from a human: Typed in by hand, Typed in based on an adventure the user has, scanned from Dungeon mag.
If I had decided on a computer-based import (reading the PCGen file, or the E:Tools file, or some "standard"), then my program wouldn't work for any of the "human" ways of creating a stat block.
If I had decided on a computer-based import, then anything that didn't create the computer file wouldn't work with my program, period (Jamis Buck NPC generator). By using a "English" standard stat block, a user can take the Jamis stat block, tweak it by hand, and then import it. If it was a computer-based format, the Jamis file wouldn't work.
That's why we need a standard.