A sanitary cross creates "crossover" of waste is "almost" impossible to snake through it. A double "combo" creates "3/4 S" traps, so the double fixture fitting is the only proper one. A "'double sanitary tee" is not necessarily a "sanitary cross". There are double sanitary tees with the two inlets one above the other and others with them a 90 degree apart.
My first boss told me about a job where he was using a flat steel tape through a closet bend. He hit an obstruction right after pushing it in, so he "pounded" it a couple of times and it continued to go in. It was a short time after that the tenant next door was pounding on the door because he had "something" coming out of his bathroom and snaking across the dining room floor. One time, I was snaking a supermarket drain from the back of the building. I had about 140' of snake in the drain, which should have put me at the front of the building, so I went outside to open the front 2 way cleanout to see if I was there yet. But when I got there, my snake had turned up from the combo, pushed the cleanout cover off and was going across the sidewalk. Some "dimestore cowboy" had "wrestled" it the ground and hogtied it around a post.