We were under the impression that "Change the target of target spell or ability with a single target" logically means:
As with all game, rules trump logic!
"target spell or ability with a single target"
is clarified by this rule:
115.9a An object that looks for a “[spell or ability] with a single target” checks the number of times any object or player was chosen as the target of that spell or ability when it was put on the stack (…)
"target spell or ability with a single target"
is clarified by this rule:
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules