not an expert on how google earth measures but my thought is unless the satellite is directly perpendicular over the two points your are measuring too the distances would vary slightly just based on geometry and the distance would be different based on the angle in the sky the satellite was off the perpendicular..
GE is an utterly amazing contraption.
Yes, one would think looking at an object obliquely and doing a measure the “true” distance” would be skewed.
I know my property and building dimensions. GE gets all those pretty close even when looking at them off perpendicular.