I wish I had the chance to fly a variant of the A-4. I flew the T-45A at NQI when I was a student. I loved A-4s when I was growing up. My ole man was an enlisted Marine and we always lived around a Marine air station so I got to see A-4s a lot. Anyways, I believe the only reason the launch bar is switched to retract after tension is just to ensure it goes up after launch and the student doesn't have to think about moving another switch once they are airborne.
Just a random comment - a lot of folks don't realize when a US Navy or Marine student goes to the carrier in the T-45 they don't have an instructor in the back seat. The student is solo. 10 traps and 4 touch n goes to become carrier qualified. Another random comment - landings in the T-45 is done with the speed brake out. The plane is underpowered and at the boat, when it hits the "burble" behind the carrier, it's prone to ramp strikes if the pilot gets slow.
For folk's that are interested, here's a link to the current T-45 Carrier Qualification Manuel
As for this T-45 mod. I've "flown" it for around an hour or so on the VNAO server. The folks that worked to make this happen did an outstanding job. Sure it's a WIP but excellent job so far!