extended release are just two doses of the drug where half the beads are delayed by ~4 hours. How is that different from taking two edibles a day and claiming full day efficacy?
The benefit is that the medication automatically produces a smooth effects profile allowing you to live your life without timing medication to perfection.
A pronounced come-up and crash is a risk factor for abuse and addiction, so smoothing or removing the peaks and valleys is important.
(As an aside, there are more complex extended release mechanisms than just delayed bead release - like lisfexamfetamine is a inactive prodrug, so cleaving the lysine off the amphetamine is rate limited. This has the effect of extended the duration of effect, and reduces the potential to abuse by snorting/iv/etc).