That's because this is "linkbait". The poster is a founder of Tapestry, the site actually hosting this content.
To be honest, I'm fine with this kind of submission, I think it's a better way to see a product in context than a "Show HN", however, some people may see it as being underhanded as it defies the convention around here.
To an extent, I see what you're saying. However, I didn't take this particular linked "tapestry" as a "join this site" mechanic. Well, I think the last slide said join or something, but I don't get the correlation at all between the content of that slide set and desiring to join the site. Is Tapestry intended to show data visualizations like this or something? I didn't get that vibe from it.
If people had concerns like these, then maybe I'd agree with you. If all people can focus on is the UX of a site, as they tend to with ANY post, be it Show HN or otherwise, I stick with me original statement.
To be honest, I'm fine with this kind of submission, I think it's a better way to see a product in context than a "Show HN", however, some people may see it as being underhanded as it defies the convention around here.