Autocompleting the selector argument type starts with all negative types, like type=!minecraft:area_effect_cloud. Even when autocompleting things like type=end, it starts with type=!ender_crystal.
This is dangerous, because you usually look at the end of the word and the exclamation mark is pretty thin. It also isn't very useful, because selecting types is more common than selecting everything not of a certain type. And lastly adding an exclamation mark in the middle should definitely not happen.