I usually don't agree with anything that slizzardman says that sounds complicated.
If you're not a bodybuilder, you don't need to worry all that much about what he's talking about. He's talking about muscle fibers being more active when they're in a better line of pull.
Lats are better developed through bent arm work. Straight arm increases the lever arm, so relative strength improvements come with very incremental improvements in time/weight. Straight arm is also hard on your elbows. This is why lateral raises and DB flyes should usually be performed with a slight elbow bend.
You need to be able to perform movements with your arms locked out with gymnastics though. I'd just focus more on the movements and their variants and not on trying to isolate a certain muscle.