I would agree they try to say what you say...not denying that. However they need to set aside therefore the Westminister Confession which says
God from all eternity, did, by the most wise and holy counsel of His own will, freely, and unchangeably ordain whatsoever comes to pass; yet so, as thereby neither is God the author of sin, nor is violence offered to the will of the creatures; nor is the liberty or contingency of second causes taken away, but rather established.
Yes they add on "...yet so as thereby neither is God the author of sin....." I'd say however they can't have it both ways. If they're going to claim he ordains whatever comes to pass that must include sin. It can't be either that well God just allows sin.....if that was their position they would be agreeing with Non-Calvinists. Ordaining must mean God creates the influence for the sin to take place but in backtracking YES they'll say God is not responsible for man's sin. The language they use they don't say responsible but they do say ordains all. Truly no difference.