Not sure what the approach of this library is, but can't you generate a nonce from a larger alphabet, hash the column values with the nonce `hash(nonce || column)`, and crypto-shred the nonce in the end.
Then, during hashing you just need a constant immutable state, which effectively expands the hash space, without incurring the mutable state overhead of replacement strings strategy.
Then, during hashing you just need a constant immutable state, which effectively expands the hash space, without incurring the mutable state overhead of replacement strings strategy.