I think they're in the process of introducing a big change for Guts, and this somewhat meaningless time they've spent on the Beast is an artificial filler inserted to rationalize that eventual change. They're giving it (page) time to manifest so it won't feel sudden.I read through the most recent episodes again, and I have to say that the whole thing with the Beast of darkness was basically useless. As Aaz and Walter previously said, its appearence in ep 373 doesn't make any sense, and it's a huge misconception about what the chains that bind it are; but besides that... what was the point of showing it? It breaks the chains in ep 371, then it mocks Guts in ep 373, and here Guts puts it back in chains. Nothing new was said by either the Beast or Guts, and the status quo hasn't changed even a bit. They really have no idea how to fill 21 pages of content. You can basically throw away half the pages in these episodes.
That makes sense to me, structurally. But unfortunately for readers, it all amounts to lip service, because each scene merely repeats the same lines from the beast that we've heard for years—nothing is being pushed forward. They're only elongating the problem each time they touch it. So yeah, it does end up feeling artificial and filler-y. Just more and more pages of Guts looking and feeling hopeless ever since Ep 368—a truly insane amount of time spent on it versus how he coped with the Eclipse.