I see lot of confusion regarding spun content.
So let me help you understand spun content.
If you spin a content and it passes copyscape and other plazarism checker doesn't mean it's not duplicate or spun content.
It still is!
So when google looks at your spun content it can figure out there's nothing new in it and it's a copy of other content , it's just "reworded".
So how much you spin it , rewrite it , rephrase it, reword it, para phrase it , it's still a duplicate content. There's nothing new, there's nothing of value for the readers.
I hope you understand now why spun content is still duplicate content. And duplicate content is a bad news for your website.
By the way the purpose of copyscape is to find out if someone is stealing you content not to steal someone's content.
Also don't fall for Quillbot para phrase bullshit. It's still duplicate content as I explained above.