The presence of nitrate extends the presence of nitrite because the nitrate slowly converts to nitrite....nitrate isn't essential in short term dry-curing and isn't as important when dry curing whole muscles as it is in dry curing sausages.
In certain situations, lack of enough cure could be dangerous (botulinum growth in dry cured sausage, etc.) if the product doesn't dry enough before all the cure is spent.
A couple other points:
As Dan said, not all cure #2 is pink...that which Butcher & Packer sells is one that's white...last I knew.
There are at least 3 different cure #2 formulas here in the USofA.
6.25% nitrite and 1% nitrate. (SausageMaker)
5.67% nitrite and 3.63% nitrate. (Butcher & Packer)
6.25% nitrate and 4% nitrate. (Allied Kenco)