Waifu Warriors: Featuring Link from the Legend of Zelda series! Now on New 3DS WOAH!

[SchAlternate]

... but the Giant's Knife is literally another term for the Biggoron Sword.

http://zelda.wikia.com/wiki/Giant%27s_Knife

Well I mean ... there's a technical difference but you know what I mean.

Not really. The Giant's Knife is the blade you get from Medigoron, and the Biggoron Sword is the one you get from, well, Biggoron. They are both as strong, but the Giant's Kinfe is significantly less sturdy, snapping in two after a few uses, while Biggoron's Sword never breaks.

Plus, one of the items you need to trade in the Biggoron's Sword sidequest is a broken sword, which looks identical to the broken Giant's Knife, but the later can't be traded to Biggoron for the ultimate sword because that'd make things much easier and convinient, implying that both swords use different alloys or something.