Clipboard manager without privacy concenrs?

All posts regarding clipboard history on mac are full of clipboard apps suggestions. However, no mention of privacy issues. I just want to know, am I missing something?

How people are comfortable with having an app that will save EVERYTHING they copy without a guarantee that these data won't be sent somewhere? Passwords, PINs, bank account numbers, etc. get copied/pasted often.

So am I missing something? Is there a technical way to tell that that app doesn't have network access for example?

Having the declaration: "The developer does not collect any data from this app." in appstore doesn't proof anything, to my knowledge.