Maybe, maybe not. I can argue that things might have been different if it had started at 3:45 instead of 4. Maybe if Ewell's attack began sooner than it did, that would have changed things. And there's evidence that the attack on the Confederate right was not intended as an echelon attack. We can micro-manage just about every incident in the war. I don't think it alters the overall assessment of the attack.
Curious what evidence you have that it wasn't intended as an echelon attack. Almost every modern historian I've read has it as that. It wasn't obviously originally intended as that, but my understanding of the timetable is
8:00 AM Johnstson comes back from his faulty scout of the Union left wing
8 - 9:00 AM Lee has meeting with Longstreet, Hill, Hood, and McLaws where we get the flanking attack up the Emmitsburg road
9:00 - 11:00 AM Lee meets with Ewell to discuss plan to coordinate with Longstreets attack
11:00 AM Lee returns, and Longstreet asks to wait on Law's brigade
1:00 PM Longstreet moves out
3:00 - 3:15ish Hood / McLaws begin moving into position and notice Union III Corps is in there way.
3:15 - 3:30 McLaws and Hood sent repeated messages to Longstreet that the predicted attack won't work.
3:30 Lee comes on scene and him and Longstreet meet and echelon attack is decided.
4:15 Echelon attack begins. Each brigade begins to step off about every 15 minutes - Law and Robertson both attack at same time.
4:20 - Benning goes into support Law
4:45 - 5:00 Anderson launches his attack
5:30 - 6:00 Kershaw goes in Supported by Semmes
6:00 - 6:15 Barksdale goes in and attacks up Emmitsburg Road / Woof attacks south to support Kershaw
6:00 - 6:30 - Wilcox, Perry, and Wright all goes in one shortly after the other continuing the echelon assault.
6:30 - 7:00 Assault breaks down as Mahone and Posey do not really engage, and Pender is mortally wounded.
7:00 - Johnson begins his assault on Culp's Hill
7:30 - Anderson, Semmes, and Kershaw are making the final attack on LRT
7:30 - Avery and Hays make there night attack on Cemetery Hill.
This is my close approximation from reading different sources as to the timetable of Day 2. Some of this is off top of my head, as I'm not at home to check my sources so may not be 100% accurate.