Salvage Stitch for Loose Ends

On this website’s instructional videos the salvage stitch shows the needle inserted for a knit stitch then slipped without working the stitch.

In “The Brand New Knotter” by Lucy Neatby the needle is inserted for a purl stitch then slipped without working it.

Does it matter which method is used?

Slipping knitwise or purlwise will look different. Try them both. If you start doing it one way and change your edge could look rather odd. Patterns usually specify if it is to be slipped knitwise, unspecified mean slip purlwise. Mainly, be consistent.