Why is this so much better of an adaptation than the anime
Because it's not skipping eighty percent of the source?
I'll grant that the dialog is a hell of a lot lighter, but vast majority of the events so far adapted in the manga have been covered in the anime. This is honestly the first moment I definitely didn't recall being in the anime. All the others were there, they just had dialog trimmed from the conversations, or the scene of the conversations merged with another scene. But I seem to recall the rest of the New Year's arc showed up in the anime, so it's really just this first part of Ch.13 that got omitted, so far. I'll be confirming soon enough as I continue my rewatch-while-reading that has resulted in me spotting nearly all the same moments in both the anime and the manga, just noting that the anime side of each moment isn't usually as fleshed out as the manga.
It's really the fact that the dialog is thinner and there's a hell of a lot less Amane internal monologue in the anime, and the expressions and shots are just so much better in the manga. It still has the same moments as the anime, they're just fleshed out much better here.
One thing I did like about the anime is the fact they didn't just default to being on the couch for most of the conversations, but that's one of the few things I appreciated about it over the manga's depiction of these moments. The manga is still overall better.