One of the existing caveats of submission editing is that calculations and summaries are static; they lose the ability to automatically update based on their original conditions. When you have calculation heavy apps this can be very tedious, if not unrealistic, to manually go through and edit each field.
If these fields stayed as variables, and updated based on changes to their reference fields, this would greatly increase the value of submission editing on apps that heavily rely on these fields.
An example of this could be as follows: An app is used to record average speed. The reporter records the time it takes for something to travel a set distance (all they record is time). The calculation field divides the set distance by the recorded time (giving a speed). If the reporter mistypes a time (lets say 100 seconds instead of 10 seconds), and submits. Later, the reporter is looking through his data and notices the anomaly and wants to fix this. However, because the calculation field does not update, changing the time field does not change the speed recorded. As a mobile user it is very possible this calculation field could be hidden or not editable, since the calculation will never change, so the reporter is unable to make the changes needed to show an accurate speed. While hypothetically someone could go onto the GoCanvas website and change the value, this quickly sees several issues with scalability, data accuracy, and logistics.
I have really only talked about calculations so far because they are what I primarily use. But, the summaries field works in a very similar manner, and I feel would go hand-in-hand with this change.
A bit of lengthy example, but I hope it provides a simple understanding of the limitations of the current design and the value that this change might bring.