Since the observer outside of space/time would be observing all that there is, I would not imagine that it would be the same as nothing at all. I would imagine it as being everything-at-all within space/time.
If a 2 dimensional man cannot see a 3 dimensional man, that does not imply the reverse. And it also suggests that the 3 dimension man sees so much more.
But, we make a terrible mistake if we imagine the one outside space/time as being human-like in abilities and perceptions. Just the discussion itself should have disavowed us of that notion.
Sadly people have this annoying tendency to anthropomorphize God into a small "god" their puny, mortal minds can comprehend.