Sorry Thomas, I should have clarified, my cabinets are frame rather than frameless like yours. I loaded a standard frameless cabinet and deleted the top, it reacts just like yours. It's a question Thermwood will have to answer for you.
Thomas
I am guessing but here are my thoughts. If you have a top and deck on an upper cabinet and you wish to put doors on it you are asked to select an opening. When you select the opening it is highlighted as that area inside the top, deck, and the two sides. YOu then set your reveals and the program installs doors based on the opening size you selected and reveals you enter. When you remove the top the openng size changes so the original doors are removed because you have removed their reference which included the top. If you reselect the opening without the top then the opening size is greater by the thickness of the top. You then have to reinstall doors which are calculated based on the new opening height. I am probably wrong as I often am but sometimes a bad explanation is better than none. THe end result is that the cabinet doors are exactlythe same in either case but removing the top is a two step process. remove the top --- reinstall doors
Removing the top of these cabinets will remove the door. however you can put it back without a top. as Ralph explained. Or you could make the top a phantom part and adjust the reveals as needed.