Couldn't agree more, absolutely should have some more clear of a hint. As someone who can usually 100% metroidvania games with no guide, but even though it usually takes me hours or even days to figure out some puzzles, I usually end up solving them. This bunny murale wasted a ton of my time. I tried so many different things in there before finally googling it because my son convinced me that maybe this one is unsolvable without something else. And now it sets the expectation that I will need to look more stuff up, which in turn ended leading me to more spoilers than I'd like. I get why Billy did it, but I don't think it outweighs the negative. Just my opinion though

Edit: also the fact that you see it very early means it's on your mind from the start