Nothing is being mixed up.

I'm not talking about literal facts.
I'm talking about prevalent attitudes amongst serious musicians and "people actually in the music business" that I have personally encountered.

The majority seem to view "songwriters" who do not sing reasonably well or play an instrument reasonably well as...pretenders. The attitude in that industry seems to be that good music comes from good musicians.

Before he made it big, Chris Stapleton was a bonafide songwriter.
Sunset Poet is a guy enjoying a hobby.
Sunset Poet can sing some songs adequately and plays guitar pretty well, so he has that.
If he could not sing or play worth beans...he would be a "pretender" to many in that business.

It is a fact that someone who cannot sing or play anything ...can write "lyrics" and sing some version of them into a cell phone recording app. Almost always sounds terrible.
BUT NOW, SUNO can blow such cat-scratchings up into a truly good and well produced recording.

Once done, such a songwriter can call themselves a "songwriter." That would be a literal fact.

But I doubt that the vast majority of people actually in the music industry would see them as anything other than a pretender or a tag-along.

Beauty is in the eye. It comes down to what a person wants to believe.

https://soundcloud.com/sunset-poet-of-texas