You are correct that there is not a way currently to move a time entry from one week to another. They can only be moved to different days within the same week. This functionality has always been the same for our time entry system.
You may have been referencing this question as it is essentially the same as yours: https://solutions.teamdynamix.com/TDClient/Forums/Questions/Details?ID=103186
The answer to that question was incorrect and is in the process of being updated at this time to reflect accurate information.
I hope this has fully answered your questions. If there is anything else I can clarify for you please let me know.