This one chapter alone is exceptional development for Guts. He really is an excellent character.
What I find most amusing is that all this "development" which has happened--and there has been a lot of development-- is happening in a flashback. While I do find it interesting seeing all of this backstory, seeing the dynamics between Guts and Griffith and how their relationship has evolved, and hopefully seeing what led them to becoming enemies, I'm really just looking forward to seeing the actual plot advance. It's been so long since we've entered this backstory that I almost forgot the more carefree, relaxed, and sociable Guts of now was at one point a drastic shift from his original (and later?) behavior.