I think his reaction, both has him validated and realize how much refusing to accept this has hurt him. I think its deeply unhealthy for someone to constantly utilize unprocessed trauma from a death of another individual for their own art, and his lashing out both times this chapter felt more like a self flagellation. As if him using his grief to further his art was also a way that he was using her death to make himself a better artist/ better art which he uses to make a living. In a way he's also trying to use her as a commodity, and every arguments he's said here was his endless justification to refuse accepting her death in a more meaningful way.
I don't think he's doing this on purpose to make better art, he refuses to process his grief ( partly because i doesn't feel valid to be grieving like if he was a family member) that cause him strong emotions, his art happends '' strong' because of this
But problem is, yakumo is a pretty tough cookie and straight out ignore it, he managed to live like a hobo for most of his life, he totally underestimate his trauma and might think that this unsolved pain is just an small inconvinience like a hole in your shoe or not having enough money for lunch, but the story show how all this will always be coming back blowing on his face when he least expect it, like how he makes a huge hissy fit at the exhibition or how he bust into tears after yotasuke's comment ( bless his soul for not reading the room and pointing out the elephant in it )
Grieving is shitty, hard, long, confusing, there is no perfect guidebook for that, and it's not a romanced thing made of classy mourning clothes and rainy burials like you saw it in pop culture, i cannot garantee that you'll get a good closure at the end, but i can assure you that you will get a bad ending if you ignore it