The upgrade does do some of what you say. Between Warninglid & Handcross there used to be two dangerous exits/rejoins to the A23 for The garden centre/4front cars and the road to Slaugham. These are now both closed off.
A new road from the Warninglid turn off now runs 50 yards parallel serving...
@ Arundel, Worthing & Lewes sections. Good news for all (most) of us that can't believe the ludicrous single lane, tinpot sections in place now. Crack on