Liner Flex is a stretching action of a bikes frame and wheelbase in reaction to encounters with bumps, dips and other external forces. This improves comfort and control and is not related to Lateral, Torsional or Bottom Bracket Flex.
With the Alter Reflex the stretching also happens when pedaling hard. In this case there is a storing and releasing, or redistribution of pedal energy improving pedaling efficiency and boosting performance.