Uh.. what? Not stretched out you say... yeah, sure, that's because there isn't that much of a story to begin with anymore.
It was pretty much just smooth sailing the entire way to this point. And now what? All we get is these filler-like chapters without substance and which entire purpose is to be "cute".
19 days have these filler-like chapters, as well, to stretch things out but instead of trying to be cute, they try to be funny - and mostly they succeed. The ACTUAL pace of the story isn't moved by these, and is still ok.
Because even though this author has more characters and also balances fluffy, comedy, and serious chapters s/he actually closes their story arcs properly and isn't afraid to have their characters openly show affection and actually talk about what they did. Here characters will say I love you and actually mention the fact they kissed instead of pretending it never happened. We don't even at least get chapters with the characters thinking about what happened. How they feel about it, what they think, etc is all a mystery and free game. Assume what you want because we sure as hell don't know either. Here we get both girls thoughts and feelings.
In Old Xian's (19 Days) defense, she started the series more of a spin-off story (the former 19 Days cover use to be the Jianyi and Zhengxi in the same outfit as the girls on this cover) consisting of 1 page funny moments in the boys' lives, but as the series gain popularity, she started creating a storyline.
I think the pace is also entirely within the author's intent. It doesn't feel dragged out to me, because the set-up to begin with wasn't tight, and, kind of like Gintama in a way, it allows for detours with both the plot, and without actually involving the plot much at all.
It's all about what kind of expectations the author sets up for us as readers to begin with, and I feel they haven't deviated much at all from those.

IM SO HAPPY THIS STORY ISNT DRAGGED OUT LIKE 19DAYS, LIKE I LOVE 19D BUT OMFG ITS SO REFRESHING TO HAVE A STORY FROM THEM THAT IS ACTUALLY GETTING SOMEWHERE
Tho 19days is getting some kinda progress not in the way Tamen is
ahhhhhhhhhhhhh
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