Ryan didn’t make a leap; that’s the literal definition of the word. First definition I found: a notice or announcement in a public medium promoting a product, service, or event or publicizing a job vacancy.
Ryan’s link to his blog is 100% an ad, IMO. So are YC portfolio job postings.
Where do you drawn the line between when a link to a blog post is / isn't an ad? Is every submission that links to any site an ad? This seems like a gray area to me.
I don't think a job posting is ever not an ad. Whether pasting a link to one's blog is or isn't for me depends on the motivation.
If the motivation is "I might forget my blog address; better record it here", it's not an ad. If the motivation is, "I want people to be able to find out more about me/drive awareness of me or the blog," it's an ad.
Ryan’s link to his blog is 100% an ad, IMO. So are YC portfolio job postings.