Just a little note to your post.
You ask: Is single page (or one page) website design bad for SEO?
And then the options to vote are: NO, it is bad or YES it is friendly
So they don't fit the question. Is is bad for SEO? Not it is Bad. Yes it is good.
One Page Applications are not so seo friendly as far as i know because of the linking and rendering of the pages. I am not quite sure about how the search engine bots use websites, but they often get lower rankings on free to use tools, which are available in the internet.