But the point of the representation is that locations can easily and unambiguously be stored in a single number, say a 64bit integer. A bit array necessarily has some overhead to specify the number of bits; something unnecessary in this proposal. Yes a standard using two bits per sector and specifying how many bits have been used in the actual representation is easier for a human to start to decipher, but it requires more information to be unambiguous and doesn't have as nice a binary representation (I'd rather have a fixed sized larger representation that the more complex one needed for an arbitrary sized bit array).