You misunderstand the meaning of that article.
"...that when you do block thin or bad content, Google prefers when you use the noindex over 404ing the page..."
They are talking about the walk around the problem of blocking pages INSTEAD of removing them.
So, if for whatever reason you don't want to delete a page and just put a 404 status on it, it's worse than putting noindex on it. Basically, what they're saying is:
- if you have thin content, DELETE it;
- if for whatever reason you don't want to delete it, put NOINDEX on it.
P.S. My suggestion still stays the same. Delete all bad content and, if you really want, put 410 gone status for that deleted content for Google to understand immediately that those pages are deleted forever, not inaccessible by mistake or something.
Hope this makes sense
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