Select Files appends the selection to current selection

I have a folder with a sub-folder and a bunch of files
If the sub- folder is currently selected and I execute a Select-Files command, it appends the selection to the selected folder rather than simply selecting the files.

It is my task to execute a Select-None as part of the command first ?
My thought of the command is that only files would be selected.

It may depend on what the full command is, but there is a DESELECTNOMATCH argument for this.