It's extremely rare to get a nib that isn't tuned pretty much perfectly if you buy a brand new pen made by one of the Japanese big 3, Pilot, Platinum and Sailor from an actual fountain pen retailer (online or brick and mortar). I've never gotten a remotely bad nib from any of those nor have I heard of someone getting a remotely bad nib from one of them.
If you buy from eBay or used elsewhere or for that matter Amazon, you do sometimes get a bad nib because someone has tried to tune one of these nibs and botched it and then decided to try and sell the pen new.
If you buy from eBay or used elsewhere or for that matter Amazon, you do sometimes get a bad nib because someone has tried to tune one of these nibs and botched it and then decided to try and sell the pen new.