1. It is deceptively simple.
2. Deceptively, it is simple.
I believe '1' means something like this: The thing/process etc., seems simple, but that is not so. The apparent is deceptive.
Does '2' mean this: When viewed from a vantage point of deception, the thing seems simple, which it is not.
You are correct about the meaning of (1). Sentence (2), however, is (I believe) ungrammatical. Not all adverbs are fit for sentence-initial position. Your interpretation of (2) is clever. If (2) were grammatical, I suppose that might be what it meant.
If you would like me to support my answer regarding the ungrammaticality of (2) with material from linguistic literature, I am willing to try to search for some, but it may take some time. I do think this is an interesting issue. ♣