dstdize population and proportions in using

[Karl Pope]

I'm using Stata v14.1 and the command -dstdize, in Example 1 in the help pdf: dstdize deaths pop age_cat, by(nation) using(1962). The data in the file 1962 are labeled as age_category and population, but population is the age adjusted proportion of the population. But it appears it has to be labeled as population to match the variable name in the main data set which is the actual populations for the age categories. It would be really helpful to have an explicit note in the help sheets that says the variable names have to be the same even though the underlying data has to be different. Or did I miss something in how to construct this command or in the help?