Pretty good explanation, but I don't believe we have to read something of God being satisfied (in 1 John 2:2, anyway) as much as something towards us (wrath), due to sin, being averted. The reason I see it this way is that up to this point John had spoken of not sinning, but that if we do we have an advocate in Christ.This is how my pea brain understands it
Propitiation = appeasement/something of GOD is satisfied--Namely, His Justice
Atonement = Man is made "At ONe" with God--To bring back into Favor/harmony
That said, I can see it both ways (as adverting wrath and as appeasing God).