If an enemy bot never went outside of the range between -0.1 and 0.3, you're right, it probably wouldn't affect accuracy much. However, say an enemy bot has a huge spike at 1.0, and you decide to fire at it, even though the enemy cannot possibly reach 1.0 with its current heading. The shot would be wasted.
So, yeah, I'm always thinking in terms of precise MEA, and thinking that I will never fire at a GF the enemy never visited. So I don't see how it's assuming anything about how much of the escape range they might actually cover - the MEA is effectively however much of the range they ever cover. There is the scaling, which I think only assumes they're not moving in a fixed pattern.
And you're right that that is a problem with a certain MEA approximation formula some people use with their GuessFactors. :-)