I recall looking at this map and seeing a competing standard. Zero-K can read two things: a particular mex config file and the underlying metal map (for reverse compatibility). The author of this map has created their own mex file format and included a gadget that applies it to the underlying metal map. This gadget loads after the ZK gadget that reads metal maps.

Add an overdrive to fix: https://github.com/ZeroK-RTS/Zero-K/tree/master/LuaRules/Configs/MetalSpots