Wiggling has no effect on your ability to attack. Wiggling on takes you out of tumbling, and you can attack while tumbling anyways. More importantly, tumbling happens AFTER the attack's knockback. In this case, you're attacking before the knockback and stun are over, so tumbling never happens.
After a lot of headaches and failed attempts, I got the d-air to shorten the distance G&W travels vertically. I'll concede that I was wrong on that account - however, it still doesn't have anything to do with wiggling, or "thrust." Like I said, wiggling won't let you d-air any sooner, and it doesn't really matter when you use the d-air as long as you're not using it almost exactly when you're going to die.
After checking other characters, the only aerials I've found so far which gimp your vertical distance are Ivysaur's down air, which doesn't involve downward movement at all - normally, it stops Ivysaur's movement altogether - and Lucario's d-air, which also stops him. The one aerial Ivysaur has that does give it downward thrust, the up-air, doesn't work. Fox's f-air normally makes him go higher when used during a jump, yet he doesn't go any further when used during an attack's knockback. Other diving attacks like Zero Suit Samus's d-air also don't change the distance you go. Not even Toon Link's works, and his is exactly like G&W's, except more extreme, because he goes higher at first and falls even faster. So it's clearly not an issue of "thrust." At this point, which aerials work seems to be completely arbitrary.
In my defense, I had no way of knowing that a small number of completely random aerials will slow you down ONLY vertically, and ONLY if you use C-stick while you hold left or right on the analog stick. There's no logical reason why it should work that way, and it completely contradicts what happens 99% of the time. I had tested various characters using different aerials thoroughly before posting in this thread (because similar threads have popped up before,) but I was doing the inputs with the control stick, because the C-stick is unresponsive at lower game speeds, and even during normal gameplay, you can mash A faster than you can mash the C-stick. Plus, most of the arguments presented were completely anecdotal, and exactly the same as the people who claim that they absolutely positively survive longer when they air dodge, even though they don't bother to test it.
We were both somewhat off the mark, but I was the one being a **** about it, so sorry about that.