Actually I have a theory about that. It's just shooting in the dark, but I kinda got the idea the mangaka had gotten bored with Obi attacks.

Like, it's easy to assign feelings to pages that don't exist and all, but as I was reading the last part, I got the feeling the fight he enjoyed most was the pointless side fight between scissors and axe guy. Just because he could introduce new savvy ways of fighting such as using the scissors case and the birch tree. Without spoilers, this new arc has the thing with Kiriha and azami is sidelined, MC is using the flute and has a bunch of other tsugumomo on the bench. Plus we are gonna have a bunch of other fights between all the various B listers, presumably none of which who are using an obi either.

as a result, I kinda get the idea he is extending the arc so he can luxuriate in the novelty of being able to use completely new fighting moves and affinity trade offs before he has to go back to the main plot which will include at least one obi user again