Now, I know that with marketplace items you can use assets royalty free, but in the description it says: “This animation set is a fantastic resource for prototyping your next project or getting your mod up and running” Note that it does not reference a commercial game anywhere in the text.
Anything you get from the marketplace is for personal or commercial use. The reason its worded that way is because the process of making a game is pretty time consuming as you probably know. So it helps to have some premade assets to test out your game fairly quickly. While you are fine tuning it you may find that a premade asset you bought or got free needs a little tweaking or you may replace it with something else. That’s all.