ME 67 Volcano Mod question

[Many Mariuses]

I picked up ME 67 yesterday. After installing the most recent patch, the Volcano man art and scenario packs, and Jison's MapMod, I discovered the following issue.

In The Volcano Man scenarios Clear and Sand hexes show a Terrain Combat Modifier of 20%. These values are also present in the Parameter Data Dialog. I would attach screenshots, but I am notified the files are too large.

Is this a typo or an error? I initially thought the modifier might be purposeful (for balance or to depict something abstractly). However, Rough Terrain has only a 5% modifier, and Broken, Forest, and Marsh hexes have a 10% modifier. I may be missing something here, but it seems odd that even the barest sort of cover would be less defensible than open terrain.

The stock scenarios are not affected, but all of the VM "alt" scenarios are. Any ideas?