By saying that is 1/3rd of a space, you are pretty much saying that the true, full space is the one found in a monospaced font. Because that 1/3rd fake space s

By saying that is 1/3rd of a space, you are pretty much saying that the true, full space is the one found in a monospaced font. Because that 1/3rd fake space space looks about the same size as the proportionally-sized real spaces you have elsewhere.