If someone wishes to write it this way, have at it. But we're back to one of those things on which we're likely to never agree. I believe that very common conventions, across many forms of documentation, for referring to number pad keys need to be known by "the average computer user." It is no help to make documentation longer, and more complicated, assuming that this is not something commonly known, in my opinion.
Asterisk as the multiply operator and slash as the divide operator predate the PC, and have been in use in that way on many adding machines for decades now, particularly after the PC appeared.
Numpad multiply and numpad divide need to be understood under those terms, and I'd rather the rare person who doesn't already know them do what Mr. Russell did and ask. There's nothing wrong with having a very occasional gap in common knowledge and asking to fill it in.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
Always remember others may hate you but those who hate you don't win unless you hate them. And then you destroy yourself.
~ Richard M. Nixon