Once you choose unique values for your feature class symbology, the parameter "Adjust Size Automatically" effects all unique values as a whole, which degrades the unique idea of unique values.
I'm aware I could split my feature class into separate ones based on the attribute being used for symbology, however this is just an administrative nightmare. Do I recombine them and split them again if I decide on another attribute field for my symbology; the parameters in the symbol editor for a specific symbol in a layer should only affect that symbol.