Well, well, well, That is a brilliant discovery. Seems like it's something new about cat behaviour.
I had always thought that cats were hardwired to bring in their trophies/kills (dead mice, rabbits, rats, birds) as a proud display of their prowess, or something.
I never for once imagined that they might think that that was what their owners liked/wanted. If the story is true, then this particular cat appears to have figured it out by a sort of trial-and-error process - "Let's see if he/she likes this...".
If one cat can do it, then it may well speak for all cats. So, positive reinforcement for the cat that brings in a "wanted" trophy, and negative reinforcement for the one that brings in an "unwanted" trophy.
Of course, a simpler explanation just might be that dead leaves may also be fun to chase and catch, because they flip about in the wind so temptingly, and as one gets older and slower, they could seem an easier catch than mice, birds, etc.