I think hard mode lowers my median score but increases the odds of an X/6.
On a typical puzzle the constraint forces me to be more thoughtful about my guesses. No playing fast and loose with consonants until I feel I know my vowels.
On a ⬛🟪🟪🟪🟪 with 4 letters that fit and 2 guesses left you could guarantee the solve without hard mode but instead you face a 50/50.