Amount of refunds is usually pretty high for all less popular games. A lot of people tend to use refunds as demo.

I doubt its that high for Stardew Valley though. Simply because popular games are sold via network effect and people ususlly know what they buying.

This doesn't seem high to me at all. You buy the game, try it for an hour, feel kind of meh on it or even just see a different game you think you'd like even more, and hit the refund button. If anything, I'm surprised it's only ~12%.