New litter box I saw

At the store yesterday and saw a covered cat litter box with plastic flap in the front like a cat door. Has anyone had any experience with one of these? I don't know if my cats would be comfortable pushing that little flap open to use it. Mouth tends to back his little butt up to the opening of the box and poops outside the box! I am curious if this might solve that problem.

 

Oh I was planning to buy the new litter box (I assumed it's new, as well, because I have never seen it before) but I didn't want to without knowing if it's worth it. So, I did some research online and not many cat-owners liked it because the cats didn't make good use of it - according to the comments. My boyfriend said we should just get one and see if the cats like it because not all cats are the same.

 

I have had many cats in the past and I do not like litter box inside my house because Im allergic to cat pee. So I had a small dog pet door put into my kitchen door that goes into the garage. I know my cats were brilliant but seriously all I had to do was call them from the garage a few times and they all learned to come through it. Then I put a litter box down and showed it to them. That was it! Those cats are all passed away. I just got a new kitten with a whole world of new challenges lol. My point being, all my past cats have gone through a flap without any problem, if that helps regarding the flap on the box. I have never liked those for my sake. They get dirty an hard to clean.