The words "nonphysical" and "supernatural" — with their prefixes "non-" and "super-" — point to what something isn't: not physical, not natural. The thing might be real and we might be able to know it somehow, but those words don't offer options.

So, yes, as I wrote:

"When we refer to a soul that is 'nonphysical' or 'supernatural,' we’re explicitly flagging the way in which it can’t be factual and can’t be known."

That is: When we choose to use those words, we explicitly flag the way in which we don't know something: not physically, not naturally.

If someone means to say something about what a soul is (rather than is not), they could use different words.