Hey David!
It's not possible to re-target users based on the X button. As AllanHeoFNM mentioned, only button 1 or button 2 clicks. Body clicks means: "Occurs when a user clicks on the message itself, and not one of the buttons." Find more in the documentation. This also can include clicks of the IAM itself, so it's not 100% sure if the re-targeting works correctly. You definitely should test this.
An alternative could be to use the new IAM Drag & Drop editor and include 3 CTAs. Here you can define the button values/settings for the re-targeting.
Or you use custom HTML IAM's where you can log the clicks with JS:
appboyBridge.logClick('0')
0 = Button 1 and 1 = Button 2
Braze has some modal templates which you can use.
Hope this helps!