You ignore the units part. log (nor any other function) doesn't miraculously remove units from the quantity it acts on, it can be used only on unitles quantities.
40 years ago I went in university i also never heard it.
That was definitely part of my course back in eighties, and we used books written decade or two earlier. As I already wrote - this a lousy chemistry, sadly, it is often taught without a second thought and deeper understanding of why it is wrong and inconsistent.
Just because it is popular doesn't mean it is correct.