From GameWatcher: “Gears 5 is a fruit of many years of labor, and a result of many years of hard-earned pedigree. Nobody knows this better than Rob Fergusson, the series’ long-standing Director. In a recent interview, he said that the game’s new Escape Mode isn’t quite as fresh as we thought.
To be more exact, Escape Mode started its life cycle as Chaos, and was initially supposed to release as part of Gears of War 4. Sadly, The Coalition had to cut Chaos from the game due to it being very unpolished and rough around the edges.”
Source: N4G PC Gears 5 Escape Mode was almost in Gears of War 4