I watched one once and laughed myself silly (trying to persuade a cat to do something is entertaining for the observers but not for the persuader.)
But with Siamese generally there actually are performance issues (though not performance competition issues). The Siamese traditionally is an extremely athletic cat, and with their hyperactive personalities they HAVE to have something to do. Whether it's mouse-catching or drapery-climbing or retrieving (or unrolling an entire roll of toilet paper), they are very busy kitties.
Where we saw the conformation-oriented breeding hurting the Siamese was in structural changes that led to orthopedic problems (not to mention the narrowing skull that made for some VERY dumb cats . . . I hate to see a stupid Siamese, it's the antithesis of the breed.) When a Siamese breaks a leg just jumping off a table, it's a terrible shame. I had one who used to leap off the tops of doors in the house (onto people's heads. We locked him up when people came to visit. He fancied himself a Stalking Panther in the Jungle.)