Moving OUs in ADUC not reflected in GPMC ??

I have created a set of Computer OUs.
There is a top-level Computer OU for the company/domain.
There are 3 site-related Computer OUs at the next level down.
PLUS, one more Computer OU at this same level for "test computers" that are put there on a transient basis.
So:
Domain Computer OU
  Site 1 Computer OU
  Site 2 Computer OU
  Site 3 Computer OU
  Test Computer OU.

After having used this structure for a time, I realized that I always do this:
1) put test computers into the Test Computer OU and link a new GPO there only.
2) Since Site 3 is the smallest, link the new GPO also to Site 3 Computer OU.
3) With good test results, add a link to Site 2 Computer OU.
4) Finally, add a link to Site 1 Computer OU or, alternately remove all the links and add one to Domain Computer OU with the same effect.

I hope that sounds reasonable enough....

Now, I figured that moving computers in and out of Test Computer OU might be a bit of a waste of time if I were going to just start yet another test.
So, I thought it might be helpful to Move Test Computer OU into Site 3 Computer OU and just leave the test computers there.

First, I removed all of the computers out of Test Computer OU - putting them into the other 3 OUs.
Next, I unlinked the current testing GPO link from the Test Computer OU.
Next, I MOVED the Test Computer OU into Site 3 Computer OU.
However, the Test Computer OU didn't show as moved in GPMC.  ????
Why might that be?
Restarting the DC didn't fix it.....

(I did get it fixed but not without some trepidation).