To some extent yes, but humans tend to make moves that follow some kind of reasoning or logic. When you play a strong opponent, it's possible that you won't see the next move that they play, but once they have played it, you can deduce the logic they used in order to make it. An engine move on the other hand can easily reject the standard strategies and can appear highly irrational. When you see this kind of move, it becomes easier to suspect cheating.

yes but the computer is just so much more powerful, as well as it makes seemingly weird moves more often, as well as it can get itself out of a "bad" line if pushed that way much easier.