I'm not sure if this is an issue or a feature, but in my case it seems like an issue. The following is applicable for V5.0.5:
I create a meeting with let's say a length of 1 hour. After that I add attendees and they receive automatically Assigned(h): 1 and Left(h): 1.
If I then adjust the length of the meeting (make it 2 hours), the field Assigned(h) and Left(h) of attendees remains with original 1h, whil I need it to become 2h. The only way to adjust the is to remove the attendees and add them again.
Is this a normal behaviour?
Yes it is expected behavior : when you create the assignment of attendees, work is proposed from meeting duration.
But it is only a proposale. You can change the value if you please.
SO there is no reason to report change of duration to assigned work as it may be expected result.
Note that you don't have to delete assignment of attendees, you can just update it.
Also note that the assigned work for meeting is only for planning : real work may always be different...