What is the token for [random:hash:?]?
It's a token for generating a random string. When you look into the implementation, you can see it's the result of hashing 55 random bytes with your selected hashing algorithm (the ? part of random:hash:?). 

Will it meet your uniqueness needs? Yes. 

Since we're talking pseudo-randomness here and the fact that hashing algorithms can produce collisions, there's a possibility of the same string being generated but it's very unlikely (unless you have a massive number of SKUs being generated).

In the unlikely event that Commerce &amp; the AutoSKU don't have the logic to prevent SKU collision (which should be there as its a unique attribute), you can always add more patterns in the token (e.g. UID) to lessen the collision possibility to effectively zero, for the number of SKUs needed by your store.