Long story short, Yes, you are correct.
Long story:
If you have an appstack say Adobe_reader_11 and you want to update this to Adobe_reader_11_B you need to select Update in the manager at the Adobe_Reader_11 appstack, it wil then create a new appstack and you need to call it Adobe_Reader_11_B. The assignments wont change automatically. This means you need to unassign the Adobe_Reader_11 appstack and assign the Adobe_reader_11_b appstack manually to the same group.
If you deside to do this at a new logon (first option when you assign, so not immediatly) the old appstack Adobe_reader_11 will be unassigned (as always). When the same user logs in then it will get the Adobe_reader_11_b appstack. Make sure to only have 1 of those appstacks assigned at any given time.