(Or more accurately that it takes edge cases for such to crop up, instead of it being a constant problem)

XCOM 2's slopes, when they show up at all, are almost always designed so you have no real reason to think of stopping anywhere on the slope. The observatory map has an excellent example, where a ramp goes up around a secondary building, and specifically the ramp starts right from the building's corner this is the exact spot one would want to position a soldier to peek around the corner from good Cover, and if you try that the soldier will not be in Cover at all and also won't engage in step-out behavior, potentially preventing you from firing on a target you were expecting to be able to fire on from there. They still see use, but they're a rarity, and their placement is a lot more considered -it wasn't just that slopes broke Cover behavior in EU/EW, it was that map designs were bad about being designed so it was a natural error to run into. XCOM 2 is much more careful about slope usage.

Xcom 2 base layout