Well, even with that aside, you do still run into the issue that Darting/Flashing Weapon specifies that you must be armed with only one weapon. Which will never be the case for a knife thrower unless you're down to your last knife, as Knife Basics means you're always armed with all knives on your person.
Darting/Flashing are pretty much incompatible with Knife Basics whether for melee or ranged; if you use knives, you pretty much have to go with Two-Weapon Fighting for extra attacks.
That makes no sense at all.
Just because a Knife fighter has access to all of his knifes at the drop of a hat, doesn't mean that he can't use the Darting/Flashing Weapon feats for extra attacks and is railroaded into taking Two-Weapon Fighting feats.
Yes, the wording of Knife Basics reads "considered armed at all times", but that shouldn't be grounds for exclusion of the Darting/Flashing Weapon feats and rather seen as the uncanny ability of a knife fighter to switch his weapons incredibly fast even in heated combat.