Apparently, when a capture event changes ownership of a morphing unit, whoever issued the original morph command gets ownership of the morph result.

You can see two incidents of that here:
1) A morphing commander is captured, but reverts to a wild state after morph completion.
2) A morphing commander is captured, then morph is cancelled and a new morph command issued by new owner. Then unit is regained by original owner via dominatrix kill, but on morph completion it becomes "loyalized" and hilarity ensues.