Contour interval in TOC

[Lohengrin]

My brother and I currently are playing East Prussia '14 and it came up that the contour interval was 50m. Offhand we thought that was a bit steep for the scale, and upon checking some of my other installed PzC games, it seems some use a 20m interval (like Moscow '41) and others also use a 50m interval (e.g. France '40). The major thing about the higher interval is the steep movement penalty incurred when moving to a hex of higher elevation which, were the 20m interval utilized, would've been spread over several hexes instead of being all in one instance. This usually means that in 50m interval games it costs even more MPs to move to a higher elevation than just the elevation difference due to larger amounts of MPs lost from the inability to pay the cost to enter the higher hex on the previous turn.

Does anyone have any insight into the basis for using the higher or lower contour intervals in the TOC? Is the scale due to limitations in the source maps used for making the game maps, or is it a judgment call by the designer?