Waiting until they were only 15 miles apart was leaving it much too late. If another a/c had made acall he'd have lost separation anyway.
Not sure you read the scenario correctly?
The 2 a/c were separated, he wanted to climb the higher one to resolve a confliction with a 3rd a/c who's not in the picture, but then the lower of the 2 CLX's asked to climb and he thought this was the higher one.
There were no 20 degrees turns involved.