I have seen the same thing in math written in different ways, and with different names. There doesn't seem to be absolute 100% conformity in mathematics over what symbol to use for some things and what to call something. For example I have seen different symbols used for compliment and transpose. The same is true for the field of statistics. I think it would be beneficial if there was 100% uniformity in names in symbols in math. I am sure there is more than 90% uniformity, but it is not 100% and that is what is needed.