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I posted a question on the forum there, hopefully I get an answer from someone official so I can find out if this is really a thing or just a placeholder page error on that store, but for now I thought I'd mention it in the forum here since that same warning doesn't seem to be prominently displayed on the GOG page.

Having PC controls makes the difference between this being a list topper that I buy day one, or being somethng that I throw on my wishlist and get it in a few years when it's under $20 so I can get a gamepad (that I don't own, or even want, and none of my toher games actually need in order to play) as well without going over what the game is actually worth.
While it states it requires a controller, you can use a keyboard to play it, though I don't believe it lists the key bindings anywhere.