

I agree with you on Demon Slayer having a lot of these moments, but Mugen Train specifically is the worst example you could give. They’re meant to be hints that it’s happening inside Rengoku’s dream. The deformed artstyle serves a purpose there, indicating that this isn’t reality, sorta like how shit behaves randomly and breaks the laws of physics in our dreams sometimes
From Library of Ruina. The song “And Then Is Heard No More” from the OST touches on similar themes, go look up the lyrics if you’re intrigued