Resource weight doesn't appear to be directly derived from max.
https://github.com/greeny/SatisfactoryTools/blob/3e867bb4a14b4979ec068be0a269418bfbb94982/src/Tools/Production/IProductionToolRequest.ts
The resource weight seems to be separate from the max value when it should be derived instead. I can't think of a single instance where you would manually set a value, such as Iron, lower than copper, yet the algorithm should still prefer using iron instead.
The resource weight is calculaded based on max map resources, so it is derived.
So then why does this happen?
I set iron lower than copper in abundance, and it still prefers to make iron wire over copper wire where iron wire is less resource efficient and less speed efficient.
Discussion was done on Discord, this is just not yet implemented feature (modifying of resource weights).