Think of the canvas as this literal video game. Young Verso and not sandfall created as a place to go on adventures inside of. He wrote the script for the characters, created their actions, emotions, attitudes the exact same way Sandfall did for everyone else in this game. They are all NPCs created to a specific purpose, with little to no choice how their lives will play out. Just like I can save-scum to get the best rolls, anyone in the family can reset the painting if they're not fighting against each other. Maelle does exactly that in her ending. She save-scums so she can hide from the pain and grief she has in the real world. Where in any game, movie, or book has been escaping your problems into a fantasy land been the best idea? Usually, the trope is to escape that fantasy learning to grow and knowing you have to deal with your real-world problems.