One Page on Page One – single page sites were red flagged?

On another thread, @Nargil said: "One page PBN sites were okay in 2012. It's not hard to completely filter them out by an algorithm. Red flags all over the place."

I am obviously a noobie with near to zero experience and knowledge and I always look up at some trusted members here. However, I am curious about Nargil's statement. Does Big G really red flagged one page sites? o_O

I tried to find —…

One Page on Page One – single page sites were red flagged?