Q: What do the front quick-disconnect endlinks actually do?

They let you choose your behavior by terrain. Connected, they keep the front end flatter and more controlled, which is what you want for daily driving, highway travel, towing, and high-speed dirt roads. Disconnected, they free up independent wheel movement and articulation for technical trails and rock ledges. You can switch between the two in minutes without tools, a capability long-time 4×4 owners expect and now have in a Tesla-focused package.