I miss the day when people used the correct terms and differentiated between reshoots and pick ups. I really do.
Oh, good point.
https://en.wikipedia.org/wiki/Pick-up_(filmmaking)
In filmmaking, a pick-up is a small, relatively minor shot filmed or recorded after the fact to augment footage already shot. When entire scenes are redone, it is referred to as a re-shoot or additional photography.
It seems like it's more a difference of degree than anything else, though. Reshoots are more likely to be reworkings or replacements of existing scenes, but they could just be new versions of existing scenes that didn't quite work for some reason (an extreme example being a reshoot to replace an actor, like in that movie where they replaced Kevin Spacey with Christopher Plummer). And post-principal photography could include both major reshoots and minor pick-ups.
Also, as people pointed out already.... Refilming any part of the movie doesn't mean that what they had was bad. It just means that during editing they realized that something wasn't working. Or maybe it did, but the writer/producer/director suddenly had an idea that might work better and deliver a better end product.
Or it could mean that what they had was bad, but they figured out how to make it better. There's nothing wrong with that. There's a saying that the first draft is always bad and it's editing that makes it good. That's an exaggeration, but there's some truth to it. Nothing is perfect right out of the gate. There's no shame in making a mistake, as long as you fix it.