The cat may also just like to poo there sometimes. We often do things because we like it/prefer it for some reason. So in such a case, you assess if it's a problem actually or not, then if it is, take the most gentle means of preventing it, like if there is a bathroom door maybe you can keep it closed. Unfortunately though there may not always be a perfect solution due to environment/situation factors. Don't know enough about what not covering their evacuation entails, depends on what all factors are involved there.
With cats unfortunately you can't just talk to them and reason with them and if there's something they are able to do and they like doing it they're not necessarily going to understand why they apparently can't/shouldn't do it, so we can't blame them for not understanding or for having preferences, what we can do is be the benevolent being who directs the situation as gently as possible. It's like when we blame a sidewalk when we trip over it, as if it could have moved out of the way or something, when we know the sidewalk isn't capable of moving. Or it's like telling a river to move, it won't work, all you can do is carefully redirect the flow. The cat really isn't in a position to know what's a problem, or be told what's a problem or what they can/can't do, and when it comes to pooping, it's a weird situation because typically animals would poo in nature where there are processes that break the poo down and you don't need to remove it manually (I mean because they didn't have hands to do so, anyway) it was how nature designed it but then we wanted to have animals live indoors with us so now they have to poo in a box that we have to manually empty, I mean who knows if that is comfortable for them, but overall they have done pretty well with it. The cat has been pretty savvy about it actually, I don't know any other animal that has had to deal with pooing in a box. Maybe the cat is trying to follow the cue of the human who uses such apparatus as the bidet in the pooing process themselves. At any rate, the cat's not in a position to take responsibility like the human can, so as the more able being it's our responsibility to be the caretakers of all creatures and give all the best life possible, as that's what we'd want done for us if the situation was reversed.