What seems missing to me from the Dordt oath that Z has cited (and from historical Reformed praxis), is something of the form:
“We promise that, if in the future we discover that that any articles or points of doctrine set forth in the Belgic Confession, the Heidelberg Catechism, or the Canons of Dort in any way disagree with the Word of God, WE WILL CHANGE THEM!”
Practically speaking, the Achilles’ heel of reformed confessions may be that, as originally written, Westminster and the 3 Forms are so close to perfect, that nobody is willing to change them! This could be one driving force behind why the common understanding of subscription has weakened. It’s just easier to subscribe less, than to fix the confessional artifacts so that full subscription is enforceable.
In my Presbyterian (OPC/PCA) tradition, I know of only the one change since the original Westminster, namely the 1789 American revision that scrubbed Theonomy. And has there ever been a change to any of the three forms? How many CRC/URC pastors actually believe that Paul is the author of Hebrews, and are willing to apply the third mark of the church to those who do not?
You may say I am a nitpicker, putting such weight on something so trivial, but isn’t that the point? Do we want full subscription, or do we want subscription to the parts of the confessions that we (individually and subjectively) determine to be nontrivial?