Fixed loading pattern ETC automatically moves / spreads when you change the task finish date.
Steps to Reproduce:
1. Create a project.
2. Add a resource to the project.
3. Create a one month task.
4. Assign the resource to the task.
5. Set the loading pattern to Fixed.
6. In the assignment weekly ETC edit the etc to 20 hours in all four weeks.
7. Now edit the task finish date and move it out one week.
Expected Result: On fixed duration tasks do not shift the ETC.
Actual Result: The ETC spreads evenly from task start to finish so now the first four weeks are not what you entered of 20 hours each.
Clarity PPM 15.x
When manually entering and updating ETC segments, changing the dates on the Task will take all assignments and reset the ETC curve data.
This behaviour has always worked in this manner.
To make a change in the behaviour for a manual update to the Task Dates and how it affects the assignments would require an enhancement to the product.
As an alternative, it would be possible to use PPM Gantt or OWB/MSP to schedule changes in Tasks.
There might be some confusion on the purpose and use of the Assignment Loading Pattern. This setting is used for the computations from auto-scheduling through PPM Gantt.
Please refer to the following documentation.