That is technically correct, and possibly optimum unless we happen to know there is a file with a shorter name available. (Otherwise the file-not-found error supersedes the printer-not-found response.)
I'm considering adding a prompt at the end of the help display (print/?), perhaps "Hit ? again to display Windows printer selection dialog". But presumably the reason why you want to see which printers are available is that you actually want to print the file to one of them. In which case, why not just use the built-in (but possibly undocumented?) "PROMPT" printer, i.e.
.print prompt=xyz.txt
You can still cancel the operation if you didn't really want to print.
So unless you think having a direct link from the help display to the printer selection dialog would be too cool for words, maybe the only enhancement needed here is to the text of the help display to note the "PROMPT" option.