Your vet seems attentive. That's a major plus. I am cautious about using behavior altering meds in man or beast. My concern is the quiet and often unnoticed side effects. You are aware of your parrot baseline. Your vet is in the loop. Those are the biggest factors. Take it one step at a time. I think your bird is a cutie. But I am basically a Grey fanatic. There's a avain trainer who has(had) a YouTube video series. One of her stars was a severely plucking CAG she rescued. I don't remember anything else. I was looking for training techniques. I do that periodically. Consider keeping a journal; Med times, dose, behavior before and after. General activity around bird and house. It will aid you and vet with dosages. You'll be able to answer a basic question. Is this a one time or recurring problem? That question is very important for human or animal medicine decisions. It will eliminate a common response; I don't know but....
I get what you're saying! We have three Greys and that's helped a lot with figuring out her behavior. For clarity, she's been plucking for years, and unfortunately it's a long-term issue. I'm solidly pro-meds when normal health precautions are taken, in part because I've experienced how life-changing medication can be for mental health conditions that look "livable" from the outside, but are very distressing to the one who is affected.
I'll self-disclose a bit to illustrate my perspective, which might be different from some: when I was a kid, I started pulling out the hair at the nape of my neck from anxiety. It isn't like people imagine, yanking it out in a burst of frustration...it's a methodical, almost self-soothing behavior that becomes habitual and absent-minded, so people don't even realize they're doing it. Very similar to the way a lot of birds tend to pluck, if you watch them: they groom, then just start pulling a feather out, then another. Or they get stressed or bored, and they try to self-regulate by doing something that feels familiar and relieves the impulse. It's weird to think that something that is destructive could be relieving, but that's what it is.
Feather plucking, nail biting, skin picking, etc..."the thing" that is done might vary between individuals, but they're all types of body-focused repetitive behaviors, or BFRBs. I encourage anyone with a plucking parrot to read about BFRBs in humans, to help understand a little more about how it might work with parrots too.
So let's say we have a beloved parrot who is an inveterate plucker. We worry about the obvious feather and skin damage, so we put plucking collars and things on birds to try to help them. Those things help to minimize the physical damage caused, but not the mental distress that led to the behavior. That's because the behavior is the secondary problem; the impulse is the primary problem, and it's still there, causing the bird stress, and now frustration too. Things like enrichment, exercise, nutrition, etc are helpful, but don't take the impulse away. Trying to resist an impulse, or being unable to do "the thing" can be really uncomfortable and persistent, fueling more stress and more need to do the behavior.
As smart as Greys are, the usual human remedy of cognitive-behavioral therapy is not a great option for them.

The other two typical interventions that get to the root of the issue, and ones that I've found to work well for me too, are:
-Incompatible activities: finding an activity that is satisfying, but that also makes you physically unable to do "the thing" at the same time. For humans, that might look like a fidget spinner to keep your hands occupied so you can't play with your hair or bite your nails. For birds, that means keeping their beak busy, like with preener toys. They get the satisfaction of doing "the thing", pulling, biting, and chewing in a way that doesn't damage them, so the impulse is relieved without the harm. My girl LOVES toys with shoelace aglets. She pops them just like she pops her feathers. (Ew)
-and medication. A lot of people think that body-focused repetitive behaviors are related to OCD. We medicate other imbalances in the body, for both humans and birds, even when there's a risk of side effects; why would we not do the same for imbalances in the brain? Either way, there is the opportunity to relieve suffering. Why wouldn't we want to do that?
I hope that gives some insight into why I and others might choose to use haldol, with all the caution of any other medication treatment. And many, many shoelace toys!