RepeatButton Behavior: Mouse move releases button?

I'm experimenting with code to monitor when a GUI.RepeatButton button is released. Here is the code as it currently stands:

 private var transactionHold : boolean = false;
 private var hasTransaction : boolean = false;
 
 function OnGUI () 
 {
     if (GUI.RepeatButton(new Rect(10, 10, 200, 50)
             , "My Button"))
     {
         transactionHold = true;
         hasTransaction = true;
     } 
     else
     {
         transactionHold = false;
     }
 
 }
 
 function Update()
 {
     if (hasTransaction && !transactionHold)
     {
         print("Process transaction");
         hasTransaction = false;
     }
 }

Case 1: I click and hold the button and don't move the mouse while the button is held down. I get one "Process transaction" message when I release the button.

Case 2: I click and hold the button, then move the mouse around while staying inside the bounds of the button. I get a whole bunch of "Process transaction" messages. While there is no visual indication of it, the button is behaving as if it is being clicked rapidly. If I stop moving the mouse, the messages stop. Move the mouse again, lots of messages.

Case 1 behavior is as expected. But can anyone explain the behavior in case 2?

[EDITED: Updated code to be more concise.]