As far as I know, when some mangaka for one reason or another are unable to deliver complete chapters on a weekly or monthly basis, whatever the pacing of the magazine is, they publish a rougher version of the chapter in the magazine and rework it for the actual volume.
It's the first time I've seen such an extreme exemple though, I even had a hard time recognizing the characters at the beginning of this arc.
You can really see the difference if you check the latest chapter compared to the first episode of this arc!

I'm so happy to see so many people are still reading skip beat!!!!! And that the scanlation team (love you guys with all my heart, you're doing so good) appearantly chose to wait for the volume to release so we get the completed pages, the last few chapters were a bit tricky to understand for me!!!! Anyways I'm just so happy that this manga still gets so much love and care, I've been reading (and re-reading!!!) for so long that it definitely has a special place in my heart <3