You don't have the goblins take that lower-right corner of the tile that bypasses the water? I think it's actually about the same number of movement points, now that I think about it.
Exactly, it doesn't really save them any movement, and Heroes I've played with have always camped a ranged character there to pick off those Gobs that make it by (often Jain, who can get there before any Gobs do). In general, they've done a really good job of limiting the Ettin movement by standing so that they don't have many places to go. And while the Master can throw, it does take a Hero failing a test, and does only move one of them.