> Even so, the prospects for exceeding current records through gene editing are slim. Today’s racehorses are already tightly optimized for speed, balancing strength against the cost of carrying additional muscle mass. Adding more muscle is relatively low-hanging fruit, and if this were the key to unlocking greater speed, selective breeding would likely already have brought it about.

It's a whole new tool in the toolbox, and can introduce mutations that didn't first arise by chance in order to be then spread with selective breeding.

What about hippogriffs?

Asking for a friend...