So I learned something today. I'd assumed someone ticked an option box for the base Firebird pedestal spoiler (RPO D80) when ordering their T/A but I looked it up and apparently a Formula or T/A (and by extension a GTA) hatchback could not be had without the Aero Wing after the facelift. Interestingly it got its own code (RPO D81) despite being a package deal. This is probably a carryover from earlier cars where you had a choice (save for the GTA notchback which could only have the pedestal spoiler for fairly obvious reasons).
To your point, I think the car needs something for visual balance...but I personally think the pedestal spoiler fulfills that need. I actually like the more subdued appearance and the spoiler probably has more practical benefit as a spoiler than the Aero Wing does as a wing. I do wonder why someone did the swap, because I gather the revised Aero Wing doesn't suffer the warping and cracking issues that '85-90 Aero Wings do due to their foam core construction and years exposed to the elements. Could be for the same reason that I like it.