- using google apps scripts does not always mean that it would have something to do with google spreadsheets
- apps script can be used independently, just like any other cloud resource viz. doc, sheet or presentation
for the most part, folks do believe there could be a ton of things that can be achieved by using apps script; however, there's also a stigma attached to that notion. whenever a conversation that involves apps script come up, it gets presumed that it would somehow, somewhere involve google sheets. more times than not, it could be true but its still only a part of what apps scripts power and not the whole.
my theory on this is that this happens because we are conditioned to invoke apps script only by first creating a google sheet (or doc, or presentation) and then navigate our way through to tools > script editor.
ergo, my recommendation would be to always create your apps script file independent of any other document that it ought to be associated with.
this should sum things up -