Here's some meandering thinking on this...
I use an iOS app called Toot! and it does something special that helped me realise a distinction from sites like this.
The Toot app has all this weird stuff in there, none of which gets in the way, none of which serves any purpose, it's just weird. For example if you click on the action menu in a user profile it has an option "scan user" which plays a cheesy robot-view style scan animation over the page. Or if you unfollow someone, their avatar animates out of the bottom of the screen like a ghostly soul leaving the body.
Anyway, in UX design there is always talk about things like "micro animations" like elastic movement of scrollable items, subtle parallaxing, etc incorporated into the ui interactions. They talk about "conversational ui" where all of the text is conversational - "oh no, there are no results for your search!..." kinda bullshit. The idea being that you are brightening up a user's day, bringing delight, and all that shit. This all ignores the hard truth that craigslist still works fine. But that's beside the point.
The distinction, I think, between these two things is warmth and coldness. Toot! is a capable but otherwise standard masto client, it's actually a bit confusing to navigate in some places - but it's got that thing where you can tell it's a small team who have fun making it - the effect is a bit like contagious laughter. On the other hand you have the UX designed, orderly implementations of fun that don't give you any indication that the thing was made by people. That's where the coldness comes from and I don't think that even registers as a factor among the people who talk about "human-centeredness" in design. Not just that you're designing for people, because why the fuck do you need to be reminded of that, but that the person(s) making something should leave some imprint of their work in that thing.
This is similar in philosophy to the physical products that show signs of use over time. Instead of putting the imprint of the makers in the mass-produced thing, they let the thing collect the imprints of the owner/user so they see themselves in it. Like early macbook pros with thin aluminium shells rather than the modern solid unibody, they collected dents over time.
I don't buy into the trope of IKEA furniture having this effect because you "build it yourself" btw. That's marketing bullshit that ignores the fact that IKEA sells because it's cheap as fuck and you can furnish a room with one trip in your hatchback. Big item garbage pick-up days should be called IKEA garbage pick-up day.
so yeah. This site is an example of coldness via simulated warmth.