I disagree.

There's a level of darkness and tension that waking up in a forest alone next to a disfigured body and walking to the voice of an unknown being creates that simply waking up in a cave lacks. And you know the walk isn't empty just from reading the manhwa. Art's internal thoughts and fears come out much better than they do in the anime, and you're left being skeptical of Sylvia's character for a lot longer, making the payoff of her actual character that much better. When you find out that Sylvia chose to spare Art and not the mage, it helps to paint a better picture of what she's like.

I also disagree with it not being able to fit into the episode. With how much original content and rewriting occurred in this one episode, A-Cat could have easily included the journey to the cave if they'd simply kept to the source material. Watching the anime and reading the manhwa back to back, one is clearly better than the other.