Umbral Shadows base effects: +2 Bandwidth from Ex-Sleeper, +2 Science, +2 Bandwidth"

Somebody please explain me what does it mean exactly?

All umbral shadows are ex-sleepers - there is no other way to get them, right?

So why not to write +4 Bandwidth on each? Is there some situation when they give you only +2 Babdwidth

or there is some Umbral Shadows that are not ex-sleeper and you get them another way?