Perhaps the technique requires a lot of additional metadata, so that you could fit a 50% full "normal" hash table in less memory than it takes to store a 99% fu

Perhaps the technique requires a lot of additional metadata, so that you could fit a 50% full "normal" hash table in less memory than it takes to store a 99% full hash table using this new approach. Thus the normal hash table can always outperform the new hash table in practice despite worse big O performance because it doesn't hit the pathological worst case except in situations where the new hash table would have run out of memory.