No but people can take advantage of that.
Creating a UI design is a better option than working for free. Main reason being is that they wont have a time limit and can spend as much time as they like on the UI design.
‘difficult to sell’ still means its sellable, and there’s a possibility that they can make money for their work. There is no possibility to make money for their work when they’re giving it out for free.
There’s an option that will get you more commissions, possibility of making Robux from it and no stress involved. And an option where you are under a time limit, cannot perform to the best of your ability, have to deal with picky customers, while you make no money. It’s an obvious choice.