The reason Calvinists are not OSAS Arminians is because they are thinking in terms of humans designing and creating things. Humans can build something, but never can humans given something free choice. Likewise, Calvinists attribute inability of their god to be able to give us sufficient grace to have the free choice so that everything must be irresistibly imposed just as man is limited in his own ability to only be able to irresistibly impose, design or make out of pre-existing materials.

Calvinists, thus, are involved in man-worship, not God worship, because the god of Calvinism can't do what God can do. They draw God down to their level instead of letting God enable us with the responsibility to Him.