| Theres another way of looking at it, whereby the abstraction isn't in the distances on the mat but in the speed of the characters.
"6 squares" or even "30 feet" (or if you like, "six seconds") can be seen as an approximation to the actual speed of the characters - clearly not all characters move at exactly the same rates. If you "lose" a square maybe you stumbled slightly, if you "gain" a square maybe you moved down a slight incline or found an extra burst of speed.
I'll agree that this isn't ideal (as such effects are repeatable due to the orientation of the grid) but it might help rationalise a little. | 
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