Notice the order God gives: He knows the end from the beginning. Why does He state it that way? Maybe because He's making the point that nothing He's done or purposed has been contingent upon our actions.
I am not sure what your point is in saying, "...nothing He's done or purposed has been contingent upon our actions." No one contends that God cannot do whatever He wishes in His good pleasure. That indeed is the focus of the larger passage from which you quoted:
"Remember this, and be assured; Recall it to mind, you transgressors. Remember the former things long past, For I am God, and there is no other; I am God, and there is no one like Me, Declaring the end from the beginning, And from ancient times things which have not been done, Saying, 'My purpose will be established, And I will accomplish all My good pleasure'; Calling a bird of prey from the east, The man of My purpose from a far country Truly I have spoken; truly I will bring it to pass. I have planned it, surely I will do it."
All of this describes God's own resoluteness in pursuing and accomplishing those things which He has said He would do. He telling the transgressors not to doubt that He will do what He has said He will do just because the things which He has said "from ancient times things which have not been done."
While this proves that God's intentions as to His own acts are not dependent upon other contingencies, it does not prove that there are no contingencies.