You just know the LSAT writers felt like real menaces when they wrote this paragraph

This is painful

Can anyone point to the section where we learn why "the only" is a sufficient condition indicator while "only" is necessary condition indicator? I'm confused by the difference

For folks who have taken the exam before or have used other textbooks/LSAT study tools - why do you think this focus on grammar is important? I'm sure there's a bigger picture but I keep wanting to move on to the LR and RC material.