The point is that while both reference counting and garbage collection are types of automatic memory management, the reverse isn't true.
From a 1976 paper on automatic memory management https://www.cs.purdue.edu/homes/hosking/690M/deutsch.pdf
"Automatic reclamation of storage no longer in use is done by the following two techniques:
* Garbage collection
* Reference counting"
Note that these are two separate items and that one is not a subset of the other (and vice versa). It is simply incorrect to call reference counting "garbage collection" when the academic and industrial practices already have explicit meanings to these two terms.