I don't think what the OP asked about has anything to do with skid patches. If both the chainring and cog have even or odd teeth, the skinny links of the chain will always hit the same teeth, and those teeth will wear faster. If you have an odd/even setup, the skinny links of the chain will alternate on the ring/cog and make for more even wear. You can see this if you are running both even, every other tooth on your chainring will be dirty.