Not just for required provisions.
*C16.04. allows for a simplified amendment process when the amendments conform to the Model Constitution. This is because the amendments were passed by the Churchwide Assembly, and the congregation is simply ratifying them.
Any time any provision is being amended to exactly match the Model Constitution, word-for-word and punctuation-for-punctuation, this is a conforming change. This can apply to both required provisions and nonrequired provisions.
However, there are certain particular exceptions:
In other words, intentional congregational decisions cannot be undone under the guise of "conforming".
Note: If using Microsoft Word, the compare feature in the review tab can be quite helpful in catching differences between the congregation's constitution and the Model Constitution.
Because conforming changes have already been approved by the Churchwide Assembly, they do not need to be approved by the synod. However, because it is easy to miss or overlook a change, it is worthwhile to have the synod review the amendments before the congregation approves them. This will save headaches when future amendments are proposed.
To find out what amendments have been made to the Model Constitution, go to the ELCA page on constitutions. There will be a list there of amendments to the Model by year.